diff --git a/doc/api/deprecations.md b/doc/api/deprecations.md
index a1d87b956d2b14..b35e4b4e4cf0ff 100644
--- a/doc/api/deprecations.md
+++ b/doc/api/deprecations.md
@@ -1058,6 +1058,9 @@ The [`util.isDate()`][] API is deprecated.
 
 <!-- YAML
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/50488
+    description: Runtime deprecation.
   - version:
     - v6.12.0
     - v4.8.6
@@ -1070,9 +1073,11 @@ changes:
     description: Documentation-only deprecation.
 -->
 
-Type: Documentation-only
+Type: Runtime
 
-The [`util.isError()`][] API is deprecated.
+The [`util.isError()`][] API is deprecated. Please use
+`Object.prototype.toString(arg) === '[object Error]' || arg instanceof Error`
+instead.
 
 ### DEP0049: `util.isFunction()`
 
diff --git a/lib/util.js b/lib/util.js
index 4f66b9ee8f9dc5..12b9c5d7c670c5 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -430,9 +430,13 @@ module.exports = {
                       'The `util.isObject` API is deprecated. Please use `typeof arg === "object"` instead.',
                       'DEP0053'),
   isDate: deprecate(types.isDate,
-                    'The `util.isDate` API is deprecated.  Please use `arg instanceof Error` instead.',
+                    'The `util.isDate API is deprecated.  Please use `arg instanceof Error` instead.',
                     'DEP0047'),
-  isError: deprecate(isError, 'The `util.isError API is deprecated.', 'DEP0048'),
+  isError: deprecate(isError,
+                     'The `util.isError` API is deprecated. ' +
+                     'Please use `ObjectPrototypeToString(e) === "[object Error]" ' +
+                     '|| e instanceof Error` instead.',
+                     'DEP0048'),
   isFunction: deprecate(isFunction, 'The `util.isFunction API is deprecated.', 'DEP0049'),
   isPrimitive: deprecate(isPrimitive, 'The `util.isPrimitive API is deprecated.', 'DEP0054'),
   log: deprecate(log, 'The `util.log API is deprecated.', 'DEP0059'),