diff --git a/docs/src/use/command-line-interface.md b/docs/src/use/command-line-interface.md
index 43c96bf16c6..9761ca9c93e 100644
--- a/docs/src/use/command-line-interface.md
+++ b/docs/src/use/command-line-interface.md
@@ -611,7 +611,7 @@ Same as [`--report-unused-disable-directives`](#--report-unused-disable-directiv
   1. `warn` (or `1`)
   1. `error` (or `2`)
 * **Multiple Arguments**: No
-* **Default Value**: By default, `linterOptions.reportUnusedDisableDirectives` configuration setting is used.
+* **Default Value**: By default, `linterOptions.reportUnusedDisableDirectives` configuration setting is used (which defaults to `"warn"`).
 
 ##### `--report-unused-disable-directives-severity` example
 
diff --git a/docs/src/use/configure/configuration-files.md b/docs/src/use/configure/configuration-files.md
index 126e71b9fa2..1616c724c66 100644
--- a/docs/src/use/configure/configuration-files.md
+++ b/docs/src/use/configure/configuration-files.md
@@ -79,7 +79,7 @@ Each configuration object contains all of the information ESLint needs to execut
     * `parserOptions` - An object specifying additional options that are passed directly to the `parse()` or `parseForESLint()` method on the parser. The available options are parser-dependent.
 * `linterOptions` - An object containing settings related to the linting process.
     * `noInlineConfig` - A Boolean value indicating if inline configuration is allowed.
-    * `reportUnusedDisableDirectives` - A severity string indicating if and how unused disable and enable directives should be tracked and reported. For legacy compatibility, `true` is equivalent to `"warn"` and `false` is equivalent to `"off"`. (default: `"off"`).
+    * `reportUnusedDisableDirectives` - A severity string indicating if and how unused disable and enable directives should be tracked and reported. For legacy compatibility, `true` is equivalent to `"warn"` and `false` is equivalent to `"off"`. (default: `"warn"`).
 * `processor` - Either an object containing `preprocess()` and `postprocess()` methods or a string indicating the name of a processor inside of a plugin (i.e., `"pluginName/processorName"`).
 * `plugins` - An object containing a name-value mapping of plugin names to plugin objects. When `files` is specified, these plugins are only available to the matching files.
 * `rules` - An object containing the configured rules. When `files` or `ignores` are specified, these rule configurations are only available to the matching files.
@@ -251,6 +251,8 @@ export default [
 ];
 ```
 
+This setting defaults to `"warn"`.
+
 You can override this setting using the [`--report-unused-disable-directives`](../command-line-interface#--report-unused-disable-directives) or the [`--report-unused-disable-directives-severity`](../command-line-interface#--report-unused-disable-directives-severity) command line options.
 
 For legacy compatibility, `true` is equivalent to `"warn"` and `false` is equivalent to `"off"`.
diff --git a/docs/src/use/configure/rules.md b/docs/src/use/configure/rules.md
index fa64e926ff9..fda9596bf33 100644
--- a/docs/src/use/configure/rules.md
+++ b/docs/src/use/configure/rules.md
@@ -339,7 +339,7 @@ export default [
         rules: {
             "no-unused-expressions": "error"
         }
-    }    
+    }
 ];
 ```
 
@@ -354,10 +354,12 @@ To report unused `eslint-disable` comments, use the `reportUnusedDisableDirectiv
 export default [
     {
         linterOptions: {
-            reportUnusedDisableDirectives: true
+            reportUnusedDisableDirectives: "error"
         }
     }
 ];
 ```
 
+This setting defaults to `"warn"`.
+
 This setting is similar to [`--report-unused-disable-directives`](../command-line-interface#--report-unused-disable-directives) and [`--report-unused-disable-directives-severity`](../command-line-interface#--report-unused-disable-directives-severity) CLI options.
diff --git a/lib/config/default-config.js b/lib/config/default-config.js
index 8a6ff820057..670096f76dd 100644
--- a/lib/config/default-config.js
+++ b/lib/config/default-config.js
@@ -42,6 +42,9 @@ exports.defaultConfig = [
             ecmaVersion: "latest",
             parser: require("espree"),
             parserOptions: {}
+        },
+        linterOptions: {
+            reportUnusedDisableDirectives: 1
         }
     },
 
diff --git a/tests/lib/cli.js b/tests/lib/cli.js
index b5dfbe7dbee..61cf996726f 100644
--- a/tests/lib/cli.js
+++ b/tests/lib/cli.js
@@ -1523,6 +1523,24 @@ describe("cli", () => {
                     assert.deepStrictEqual(log.error.firstCall.args, ["The --report-unused-disable-directives option and the --report-unused-disable-directives-severity option cannot be used together."], "has the right text to log.error");
                     assert.strictEqual(exitCode, 2, "exit code should be 2");
                 });
+
+                it("warns by default in flat config only", async () => {
+                    const exitCode = await cli.execute(`${useFlatConfig ? "--no-config-lookup" : "--no-eslintrc"} --rule "'no-console': 'error'"`,
+                        "foo(); // eslint-disable-line no-console",
+                        useFlatConfig);
+
+                    if (useFlatConfig) {
+                        assert.strictEqual(log.error.callCount, 0, "log.error should not be called");
+                        assert.strictEqual(log.info.callCount, 1, "log.info is called once");
+                        assert.ok(log.info.firstCall.args[0].includes("Unused eslint-disable directive (no problems were reported from 'no-console')"), "has correct message about unused directives");
+                        assert.ok(log.info.firstCall.args[0].includes("0 errors and 1 warning"), "has correct error and warning count");
+                        assert.strictEqual(exitCode, 0, "exit code should be 0");
+                    } else {
+                        assert.strictEqual(log.error.callCount, 0, "log.error should not be called");
+                        assert.strictEqual(log.info.callCount, 0, "log.info should not be called");
+                        assert.strictEqual(exitCode, 0, "exit code should be 0");
+                    }
+                });
             });
         });
 
diff --git a/tests/lib/config/flat-config-array.js b/tests/lib/config/flat-config-array.js
index 6bc5a92278d..945f5b39ded 100644
--- a/tests/lib/config/flat-config-array.js
+++ b/tests/lib/config/flat-config-array.js
@@ -190,6 +190,9 @@ describe("FlatConfigArray", () => {
                     parser: `espree@${espree.version}`,
                     parserOptions: {}
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 processor: void 0
             };
             const actual = config.toJSON();
@@ -222,6 +225,9 @@ describe("FlatConfigArray", () => {
                     parser: `espree@${espree.version}`,
                     parserOptions: {}
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 processor: void 0
             };
             const actual = config.toJSON();
@@ -256,6 +262,9 @@ describe("FlatConfigArray", () => {
                     parser: `espree@${espree.version}`,
                     parserOptions: {}
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 processor: void 0
             };
             const actual = config.toJSON();
@@ -353,6 +362,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: void 0
             });
@@ -384,6 +396,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: void 0
             });
@@ -415,6 +430,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: void 0
             });
@@ -444,6 +462,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: void 0
             });
@@ -513,6 +534,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: "custom-processor"
             });
@@ -540,6 +564,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: "custom-processor"
             });
@@ -571,6 +598,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: "custom-processor@1.2.3"
             });
@@ -600,6 +630,9 @@ describe("FlatConfigArray", () => {
                     parserOptions: {},
                     sourceType: "module"
                 },
+                linterOptions: {
+                    reportUnusedDisableDirectives: 1
+                },
                 plugins: ["@"],
                 processor: "custom-processor@1.2.3"
             });
diff --git a/tests/lib/linter/linter.js b/tests/lib/linter/linter.js
index eddc1387f6f..167af31526a 100644
--- a/tests/lib/linter/linter.js
+++ b/tests/lib/linter/linter.js
@@ -10590,7 +10590,8 @@ describe("Linter with FlatConfigArray", () => {
                             },
                             rules: {
                                 "test/checker": "error"
-                            }
+                            },
+                            linterOptions: { reportUnusedDisableDirectives: 0 }
                         };
 
                         const problems = linter.verify(code, config);
@@ -10725,7 +10726,7 @@ describe("Linter with FlatConfigArray", () => {
                             "/*eslint-enable*/"
                         ].join("\n");
 
-                        const config = { rules: { "no-alert": 1 } };
+                        const config = { rules: { "no-alert": 1 }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                         const messages = linter.verify(code, config, filename);
                         const suppressedMessages = linter.getSuppressedMessages();
@@ -10987,7 +10988,7 @@ var a = "test2";
                         "console.log(\"foo\");",
                         "/* eslint-enable quotes */"
                     ].join("\n");
-                    const config = { rules: { quotes: 2 } };
+                    const config = { rules: { quotes: 2 }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11032,7 +11033,7 @@ var a = "test2";
                         "/*eslint-enable no-console */",
                         "alert('test');"
                     ].join("\n");
-                    const config = { rules: { "no-alert": 1, "no-console": 1 } };
+                    const config = { rules: { "no-alert": 1, "no-console": 1 }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11096,7 +11097,7 @@ var a = "test2";
 
                         "/*eslint-enable*/"
                     ].join("\n");
-                    const config = { rules: { "no-alert": 1, "no-console": 1 } };
+                    const config = { rules: { "no-alert": 1, "no-console": 1 }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11135,7 +11136,7 @@ var a = "test2";
                         "console.log('test');", // here
                         "/*eslint-enable no-console */"
                     ].join("\n");
-                    const config = { rules: { "no-alert": 1, "no-console": 1 } };
+                    const config = { rules: { "no-alert": 1, "no-console": 1 }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11174,7 +11175,7 @@ var a = "test2";
                         "console.log('test');", // here
                         "/*eslint-enable no-console */"
                     ].join("\n");
-                    const config = { rules: { "no-alert": "warn", "no-console": "warn" } };
+                    const config = { rules: { "no-alert": "warn", "no-console": "warn" }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11203,7 +11204,7 @@ var a = "test2";
                         "var bar;",
                         "/* eslint-enable no-unused-vars */" // here
                     ].join("\n");
-                    const config = { rules: { "no-unused-vars": 2 } };
+                    const config = { rules: { "no-unused-vars": 2 }, linterOptions: { reportUnusedDisableDirectives: 0 } };
 
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11603,7 +11604,8 @@ var a = "test2";
                     const config = {
                         rules: {
                             "no-alert": 1
-                        }
+                        },
+                        linterOptions: { reportUnusedDisableDirectives: 0 }
                     };
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11667,7 +11669,8 @@ var a = "test2";
                         rules: {
                             "no-alert": 1,
                             "no-console": 1
-                        }
+                        },
+                        linterOptions: { reportUnusedDisableDirectives: 0 }
                     };
                     const messages = linter.verify(code, config, filename);
                     const suppressedMessages = linter.getSuppressedMessages();
@@ -11690,7 +11693,8 @@ var a = "test2";
                         rules: {
                             "no-alert": 1,
                             "no-console": 1
-                        }
+                        },
+                        linterOptions: { reportUnusedDisableDirectives: 0 }
                     };
                     const messages = linter.verify(code, config, filename);
 
@@ -12095,7 +12099,7 @@ var a = "test2";
                     /*eslint-enable no-redeclare -- no-unused-vars */
                     var aaa = {}
                     var aaa = {}
-                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" } });
+                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" }, linterOptions: { reportUnusedDisableDirectives: 0 } });
                     const suppressedMessages = linter.getSuppressedMessages();
 
                     // Do include `no-redeclare` but not `no-unused-vars`
@@ -12135,7 +12139,7 @@ var a = "test2";
                     const messages = linter.verify(`
                     var aaa = {} //eslint-disable-line no-redeclare -- no-unused-vars
                     var aaa = {} //eslint-disable-line no-redeclare -- no-unused-vars
-                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" } });
+                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" }, linterOptions: { reportUnusedDisableDirectives: 0 } });
                     const suppressedMessages = linter.getSuppressedMessages();
 
                     // Do include `no-unused-vars` but not `no-redeclare`
@@ -12175,7 +12179,7 @@ var a = "test2";
                     const messages = linter.verify(`
                     var aaa = {} /*eslint-disable-line no-redeclare -- no-unused-vars */
                     var aaa = {} /*eslint-disable-line no-redeclare -- no-unused-vars */
-                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" } });
+                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" }, linterOptions: { reportUnusedDisableDirectives: 0 } });
                     const suppressedMessages = linter.getSuppressedMessages();
 
                     // Do include `no-unused-vars` but not `no-redeclare`
@@ -12217,7 +12221,7 @@ var a = "test2";
                     var aaa = {}
                     //eslint-disable-next-line no-redeclare -- no-unused-vars
                     var aaa = {}
-                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" } });
+                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" }, linterOptions: { reportUnusedDisableDirectives: 0 } });
                     const suppressedMessages = linter.getSuppressedMessages();
 
                     // Do include `no-unused-vars` but not `no-redeclare`
@@ -12259,7 +12263,7 @@ var a = "test2";
                     var aaa = {}
                     /*eslint-disable-next-line no-redeclare -- no-unused-vars */
                     var aaa = {}
-                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" } });
+                `, { rules: { "no-redeclare": "error", "no-unused-vars": "error" }, linterOptions: { reportUnusedDisableDirectives: 0 } });
                     const suppressedMessages = linter.getSuppressedMessages();
 
                     // Do include `no-unused-vars` but not `no-redeclare`
@@ -13401,7 +13405,7 @@ var a = "test2";
                     assert.strictEqual(suppressedMessages[1].suppressions.length, 1);
                 });
 
-                it("reports problems for unused eslint-disable comments (warn)", () => {
+                it("reports problems for unused eslint-disable comments (warn, explicitly set)", () => {
                     const messages = linter.verify("/* eslint-disable */", {}, { reportUnusedDisableDirectives: "warn" });
                     const suppressedMessages = linter.getSuppressedMessages();
 
@@ -13426,6 +13430,31 @@ var a = "test2";
                     assert.strictEqual(suppressedMessages.length, 0);
                 });
 
+                it("reports problems for unused eslint-disable comments (warn by default)", () => {
+                    const messages = linter.verify("/* eslint-disable */", {});
+                    const suppressedMessages = linter.getSuppressedMessages();
+
+                    assert.deepStrictEqual(
+                        messages,
+                        [
+                            {
+                                ruleId: null,
+                                message: "Unused eslint-disable directive (no problems were reported).",
+                                line: 1,
+                                column: 1,
+                                fix: {
+                                    range: [0, 20],
+                                    text: " "
+                                },
+                                severity: 1,
+                                nodeType: null
+                            }
+                        ]
+                    );
+
+                    assert.strictEqual(suppressedMessages.length, 0);
+                });
+
                 describe("autofix", () => {
                     const alwaysReportsRule = {
                         create(context) {