diff --git a/tools/eslint-rules/crypto-check.js b/tools/eslint-rules/crypto-check.js
index fbc319f964c696..151815cd645642 100644
--- a/tools/eslint-rules/crypto-check.js
+++ b/tools/eslint-rules/crypto-check.js
@@ -23,8 +23,8 @@ const bindingModules = cryptoModules.concat(['tls_wrap']);
 module.exports = function(context) {
   const missingCheckNodes = [];
   const requireNodes = [];
-  var commonModuleNode = null;
-  var hasSkipCall = false;
+  let commonModuleNode = null;
+  let hasSkipCall = false;
 
   function testCryptoUsage(node) {
     if (utils.isRequired(node, requireModules) ||
diff --git a/tools/eslint-rules/eslint-check.js b/tools/eslint-rules/eslint-check.js
index 00a5234733ec05..340a63ab4a00da 100644
--- a/tools/eslint-rules/eslint-check.js
+++ b/tools/eslint-rules/eslint-check.js
@@ -14,8 +14,8 @@ const msg = 'Please add a skipIfEslintMissing() call to allow this test to ' +
 
 module.exports = function(context) {
   const missingCheckNodes = [];
-  var commonModuleNode = null;
-  var hasEslintCheck = false;
+  let commonModuleNode = null;
+  let hasEslintCheck = false;
 
   function testEslintUsage(context, node) {
     if (utils.isRequired(node, ['../../tools/node_modules/eslint'])) {
diff --git a/tools/eslint-rules/inspector-check.js b/tools/eslint-rules/inspector-check.js
index 189b023efc6195..3d3c97b5c631fa 100644
--- a/tools/eslint-rules/inspector-check.js
+++ b/tools/eslint-rules/inspector-check.js
@@ -15,8 +15,8 @@ const msg = 'Please add a skipIfInspectorDisabled() call to allow this ' +
 
 module.exports = function(context) {
   const missingCheckNodes = [];
-  var commonModuleNode = null;
-  var hasInspectorCheck = false;
+  let commonModuleNode = null;
+  let hasInspectorCheck = false;
 
   function testInspectorUsage(context, node) {
     if (utils.isRequired(node, ['inspector'])) {
diff --git a/tools/eslint-rules/no-unescaped-regexp-dot.js b/tools/eslint-rules/no-unescaped-regexp-dot.js
index 3af514d4bb91a9..e9349713bfa3fa 100644
--- a/tools/eslint-rules/no-unescaped-regexp-dot.js
+++ b/tools/eslint-rules/no-unescaped-regexp-dot.js
@@ -11,8 +11,8 @@
 module.exports = function(context) {
   const sourceCode = context.getSourceCode();
   const regexpStack = [];
-  var regexpBuffer = [];
-  var inRegExp = false;
+  let regexpBuffer = [];
+  let inRegExp = false;
 
   function report(node, startOffset) {
     const indexOfDot = sourceCode.getIndexFromLoc(node.loc.start) + startOffset;
@@ -25,13 +25,13 @@ module.exports = function(context) {
 
   const allowedModifiers = ['+', '*', '?', '{'];
   function checkRegExp(nodes) {
-    var escaping = false;
-    var inCharClass = false;
-    for (var n = 0; n < nodes.length; ++n) {
+    let escaping = false;
+    let inCharClass = false;
+    for (let n = 0; n < nodes.length; ++n) {
       const pair = nodes[n];
       const node = pair[0];
       const str = pair[1];
-      for (var i = 0; i < str.length; ++i) {
+      for (let i = 0; i < str.length; ++i) {
         switch (str[i]) {
           case '[':
             if (!escaping)
@@ -96,7 +96,7 @@ module.exports = function(context) {
                         node.quasis.length);
     if (inRegExp &&
         (isTemplate || (typeof node.value === 'string' && node.value.length))) {
-      var p = node.parent;
+      let p = node.parent;
       while (p && p.type === 'BinaryExpression') {
         p = p.parent;
       }
@@ -105,7 +105,7 @@ module.exports = function(context) {
           p.callee.name === 'RegExp') {
         if (isTemplate) {
           const quasis = node.quasis;
-          for (var i = 0; i < quasis.length; ++i) {
+          for (let i = 0; i < quasis.length; ++i) {
             const el = quasis[i];
             if (el.type === 'TemplateElement' && el.value && el.value.cooked)
               regexpBuffer.push([el, el.value.cooked]);
diff --git a/tools/eslint-rules/prefer-assert-iferror.js b/tools/eslint-rules/prefer-assert-iferror.js
index 399ee7403a6c88..2129600e2d4eea 100644
--- a/tools/eslint-rules/prefer-assert-iferror.js
+++ b/tools/eslint-rules/prefer-assert-iferror.js
@@ -10,7 +10,7 @@ const utils = require('./rules-utils.js');
 module.exports = {
   create(context) {
     const sourceCode = context.getSourceCode();
-    var assertImported = false;
+    let assertImported = false;
 
     function hasSameTokens(nodeA, nodeB) {
       const aTokens = sourceCode.getTokens(nodeA);
diff --git a/tools/eslint-rules/required-modules.js b/tools/eslint-rules/required-modules.js
index a0511e0579d911..5175d4d46d7e95 100644
--- a/tools/eslint-rules/required-modules.js
+++ b/tools/eslint-rules/required-modules.js
@@ -12,7 +12,7 @@ const path = require('path');
 
 module.exports = function(context) {
   // trim required module names
-  var requiredModules = context.options;
+  const requiredModules = context.options;
   const isESM = context.parserOptions.sourceType === 'module';
 
   const foundModules = [];
@@ -46,7 +46,7 @@ module.exports = function(context) {
    * @returns {undefined|String} required module name or undefined
    */
   function getRequiredModuleName(str) {
-    var value = path.basename(str);
+    const value = path.basename(str);
 
     // Check if value is in required modules array
     return requiredModules.indexOf(value) !== -1 ? value : undefined;
@@ -70,7 +70,7 @@ module.exports = function(context) {
   const rules = {
     'Program:exit'(node) {
       if (foundModules.length < requiredModules.length) {
-        var missingModules = requiredModules.filter(
+        const missingModules = requiredModules.filter(
           (module) => foundModules.indexOf(module) === -1
         );
         missingModules.forEach((moduleName) => {
@@ -86,7 +86,7 @@ module.exports = function(context) {
 
   if (isESM) {
     rules.ImportDeclaration = (node) => {
-      var requiredModuleName = getRequiredModuleName(node.source.value);
+      const requiredModuleName = getRequiredModuleName(node.source.value);
       if (requiredModuleName) {
         foundModules.push(requiredModuleName);
       }
@@ -94,7 +94,7 @@ module.exports = function(context) {
   } else {
     rules.CallExpression = (node) => {
       if (isRequireCall(node)) {
-        var requiredModuleName = getRequiredModuleNameFromCall(node);
+        const requiredModuleName = getRequiredModuleNameFromCall(node);
 
         if (requiredModuleName) {
           foundModules.push(requiredModuleName);
diff --git a/tools/eslint-rules/rules-utils.js b/tools/eslint-rules/rules-utils.js
index c64b16479920dd..b85425cb50d59c 100644
--- a/tools/eslint-rules/rules-utils.js
+++ b/tools/eslint-rules/rules-utils.js
@@ -24,7 +24,7 @@ module.exports.isRequired = function(node, modules) {
 * Return true if common module is required
 * in AST Node under inspection
 */
-var commonModuleRegExp = new RegExp(/^(\.\.\/)*common(\.js)?$/);
+const commonModuleRegExp = new RegExp(/^(\.\.\/)*common(\.js)?$/);
 module.exports.isCommonModule = function(node) {
   return node.callee.name === 'require' &&
          node.arguments.length !== 0 &&
@@ -63,7 +63,7 @@ module.exports.usesCommonProperty = function(node, properties) {
  * and the block also has a call to skip.
  */
 module.exports.inSkipBlock = function(node) {
-  var hasSkipBlock = false;
+  let hasSkipBlock = false;
   if (node.test &&
       node.test.type === 'UnaryExpression' &&
       node.test.operator === '!') {
diff --git a/tools/lint-js.js b/tools/lint-js.js
index 807c7d9d85f62b..45941d8ceb4971 100644
--- a/tools/lint-js.js
+++ b/tools/lint-js.js
@@ -25,24 +25,24 @@ if (process.argv.indexOf('-F') !== -1)
 const cli = new CLIEngine(cliOptions);
 
 if (cluster.isMaster) {
-  var numCPUs = 1;
+  let numCPUs = 1;
   const paths = [];
-  var files = null;
-  var totalPaths = 0;
-  var failures = 0;
-  var successes = 0;
-  var lastLineLen = 0;
-  var curPath = 'Starting ...';
-  var showProgress = true;
+  let files = null;
+  let totalPaths = 0;
+  let failures = 0;
+  let successes = 0;
+  let lastLineLen = 0;
+  let curPath = 'Starting ...';
+  let showProgress = true;
   const globOptions = {
     nodir: true
   };
   const workerConfig = {};
-  var startTime;
-  var formatter;
-  var outFn;
-  var fd;
-  var i;
+  let startTime;
+  let formatter;
+  let outFn;
+  let fd;
+  let i;
 
   // Check if spreading work among all cores/cpus
   if (process.argv.indexOf('-J') !== -1)
@@ -169,7 +169,7 @@ if (cluster.isMaster) {
       // We either just started or we have no more files to lint for the current
       // path. Find the next path that has some files to be linted.
       while (paths.length) {
-        var dir = paths.shift();
+        let dir = paths.shift();
         curPath = dir;
         const patterns = cli.resolveFileGlobPatterns([dir]);
         dir = path.resolve(patterns[0]);
@@ -188,7 +188,7 @@ if (cluster.isMaster) {
     // workers busy most of the time instead of only a minority doing most of
     // the work.
     const sliceLen = Math.min(maxWorkload, Math.ceil(files.length / numCPUs));
-    var slice;
+    let slice;
     if (sliceLen === files.length) {
       // Micro-optimization to avoid splicing to an empty array
       slice = files;
@@ -212,10 +212,10 @@ if (cluster.isMaster) {
     const secs = `${elapsed % 60}`.padStart(2, '0');
     const passed = `${successes}`.padStart(6);
     const failed = `${failures}`.padStart(6);
-    var pct = Math.ceil(((totalPaths - paths.length) / totalPaths) * 100);
-    pct = `${pct}`.padStart(3);
+    let pct = `${Math.ceil(((totalPaths - paths.length) / totalPaths) * 100)}`;
+    pct = pct.padStart(3);
 
-    var line = `[${mins}:${secs}|%${pct}|+${passed}|-${failed}]: ${curPath}`;
+    let line = `[${mins}:${secs}|%${pct}|+${passed}|-${failed}]: ${curPath}`;
 
     // Truncate line like cpplint does in case it gets too long
     if (line.length > 75)
@@ -229,7 +229,7 @@ if (cluster.isMaster) {
 } else {
   // Worker
 
-  var config = {};
+  let config = {};
   process.on('message', (files) => {
     if (files instanceof Array) {
       // Lint some files
@@ -246,7 +246,7 @@ if (cluster.isMaster) {
         // Silence warnings for files with no errors while keeping the "ok"
         // status
         if (report.warningCount > 0) {
-          for (var i = 0; i < results.length; ++i) {
+          for (let i = 0; i < results.length; ++i) {
             const result = results[i];
             if (result.errorCount === 0 && result.warningCount > 0) {
               result.warningCount = 0;