diff --git a/packages/keyring-controller/src/KeyringController.test.ts b/packages/keyring-controller/src/KeyringController.test.ts
index 018c136539..48b1130f61 100644
--- a/packages/keyring-controller/src/KeyringController.test.ts
+++ b/packages/keyring-controller/src/KeyringController.test.ts
@@ -11,6 +11,7 @@ import {
   SignTypedDataVersion,
   encrypt,
 } from '@metamask/eth-sig-util';
+import SimpleKeyring from '@metamask/eth-simple-keyring/dist/simple-keyring';
 import type { EthKeyring } from '@metamask/keyring-api';
 import { wordlist } from '@metamask/scure-bip39/dist/wordlists/english';
 import type { KeyringClass } from '@metamask/utils';
@@ -100,6 +101,32 @@ describe('KeyringController', () => {
           }),
       ).toThrow(KeyringControllerError.UnsupportedEncryptionKeyExport);
     });
+
+    it('allows overwriting the built-in Simple keyring builder', async () => {
+      const mockSimpleKeyringBuilder =
+        // @ts-expect-error The simple keyring doesn't yet conform to the KeyringClass type
+        buildKeyringBuilderWithSpy(SimpleKeyring);
+      await withController(
+        { keyringBuilders: [mockSimpleKeyringBuilder] },
+        async ({ controller }) => {
+          await controller.addNewKeyring(KeyringTypes.simple);
+
+          expect(mockSimpleKeyringBuilder).toHaveBeenCalledTimes(1);
+        },
+      );
+    });
+
+    it('allows overwriting the built-in HD keyring builder', async () => {
+      const mockHdKeyringBuilder = buildKeyringBuilderWithSpy(HDKeyring);
+      await withController(
+        { keyringBuilders: [mockHdKeyringBuilder] },
+        async () => {
+          // This is called as part of initializing the controller
+          // because the first keyring is assumed to always be an HD keyring
+          expect(mockHdKeyringBuilder).toHaveBeenCalledTimes(1);
+        },
+      );
+    });
   });
 
   describe('addNewAccount', () => {
@@ -3538,3 +3565,21 @@ async function withController<ReturnValue>(
     messenger,
   });
 }
+
+/**
+ * Construct a keyring builder with a spy.
+ *
+ * @param KeyringConstructor - The constructor to use for building the keyring.
+ * @returns A keyring builder that uses `jest.fn()` to spy on invocations.
+ */
+function buildKeyringBuilderWithSpy(KeyringConstructor: KeyringClass<Json>): {
+  (): EthKeyring<Json>;
+  type: string;
+} {
+  const keyringBuilderWithSpy: { (): EthKeyring<Json>; type?: string } = jest
+    .fn()
+    .mockImplementation((...args) => new KeyringConstructor(...args));
+  keyringBuilderWithSpy.type = KeyringConstructor.type;
+  // Not sure why TypeScript isn't smart enough to infer that `type` is set here.
+  return keyringBuilderWithSpy as { (): EthKeyring<Json>; type: string };
+}
diff --git a/packages/keyring-controller/src/KeyringController.ts b/packages/keyring-controller/src/KeyringController.ts
index 1d657295ad..4979f4f7e0 100644
--- a/packages/keyring-controller/src/KeyringController.ts
+++ b/packages/keyring-controller/src/KeyringController.ts
@@ -611,7 +611,7 @@ export class KeyringController extends BaseController<
     });
 
     this.#keyringBuilders = keyringBuilders
-      ? defaultKeyringBuilders.concat(keyringBuilders)
+      ? keyringBuilders.concat(defaultKeyringBuilders)
       : defaultKeyringBuilders;
 
     this.#encryptor = encryptor;