diff --git a/lib/node-gyp.js b/lib/node-gyp.js
index 26fcb2ee49..dafce99d49 100644
--- a/lib/node-gyp.js
+++ b/lib/node-gyp.js
@@ -133,24 +133,25 @@ class Gyp extends EventEmitter {
     //   other tools.
     // The `npm_package_config_node_gyp_` prefix will take precedence over
     // `npm_config_` keys.
-    const npmConfigPrefix = 'npm_config_'
-    const npmPackageConfigPrefix = 'npm_package_config_node_gyp_'
+    const npmConfigPrefix = /^npm_config_/i
+    const npmPackageConfigPrefix = /^npm_package_config_node_gyp_/i
 
     const configEnvKeys = Object.keys(process.env)
-      .filter((k) => k.startsWith(npmConfigPrefix) || k.startsWith(npmPackageConfigPrefix))
+      .filter((k) => npmConfigPrefix.test(k) || npmPackageConfigPrefix.test(k))
       // sort so that npm_package_config_node_gyp_ keys come last and will override
-      .sort((a) => a.startsWith(npmConfigPrefix) ? -1 : 1)
+      .sort((a) => npmConfigPrefix.test(a) ? -1 : 1)
 
     for (const key of configEnvKeys) {
       // add the user-defined options to the config
-      const name = key.startsWith(npmConfigPrefix)
-        ? key.substring(npmConfigPrefix.length)
-        : key.substring(npmPackageConfigPrefix.length)
+      const name = npmConfigPrefix.test(key)
+        ? key.replace(npmConfigPrefix, '')
+        : key.replace(npmPackageConfigPrefix, '')
       // gyp@741b7f1 enters an infinite loop when it encounters
       // zero-length options so ensure those don't get through.
       if (name) {
         // convert names like force_process_config to force-process-config
-        this.opts[name.replaceAll('_', '-')] = process.env[key]
+        // and convert to lowercase
+        this.opts[name.replaceAll('_', '-').toLowerCase()] = process.env[key]
       }
     }
 
diff --git a/test/test-options.js b/test/test-options.js
index 8ea616fd1a..e14f827d56 100644
--- a/test/test-options.js
+++ b/test/test-options.js
@@ -30,6 +30,9 @@ describe('options', function () {
     process.env.npm_config_y = '41'
     // Package config should take precedence over npm_config_ keys.
     process.env.npm_package_config_node_gyp_y = '42'
+    // All configs should be case-insensitive.
+    process.env.NPM_PACKAGE_CONFIG_NODE_GYP_XX = 'value'
+    process.env.NPM_CONFIG_YY = 'value'
     // loglevel does not get added to opts but will change the logger's level.
     process.env.npm_config_loglevel = 'silly'
 
@@ -41,10 +44,12 @@ describe('options', function () {
 
     assert.strictEqual(log.logger.level.id, 'silly')
 
-    assert.deepStrictEqual(Object.keys(g.opts).sort(), [...keys, 'argv', 'x', 'y', 'foo'].sort())
+    assert.deepStrictEqual(Object.keys(g.opts).sort(), [...keys, 'argv', 'x', 'y', 'foo', 'xx', 'yy'].sort())
     assert.strictEqual(g.opts['x'], '42')
     assert.strictEqual(g.opts['y'], '42')
     assert.strictEqual(g.opts['foo'], '42')
+    assert.strictEqual(g.opts['xx'], 'value')
+    assert.strictEqual(g.opts['yy'], 'value')
   })
 
   it('options with spaces in environment', () => {