diff --git a/index.js b/index.js
index e370bbebf..a29526bf4 100644
--- a/index.js
+++ b/index.js
@@ -26,11 +26,13 @@ class ServerlessWebpack {
     this.options = options;
 
     if (
-      (_.has(this.serverless, 'service.custom.webpack') &&
-        _.isString(this.serverless.service.custom.webpack) &&
-        _.endsWith(this.serverless.service.custom.webpack, '.ts')) ||
-      (_.has(this.serverless, 'service.custom.webpack.webpackConfig') &&
-        _.endsWith(this.serverless.service.custom.webpack.webpackConfig, '.ts'))
+      (
+        (_.has(this.serverless, 'service.custom.webpack') &&
+          _.isString(this.serverless.service.custom.webpack) &&
+          _.endsWith(this.serverless.service.custom.webpack, '.ts')) ||
+        (_.has(this.serverless, 'service.custom.webpack.webpackConfig') &&
+          _.endsWith(this.serverless.service.custom.webpack.webpackConfig, '.ts'))
+      ) && !process[Symbol.for('ts-node.register.instance')]
     ) {
       try {
         require('ts-node/register');
diff --git a/index.test.js b/index.test.js
index 585e8b70a..ef4ef3a99 100644
--- a/index.test.js
+++ b/index.test.js
@@ -80,6 +80,15 @@ describe('ServerlessWebpack', () => {
       expect(Module._load).to.have.been.calledWith('ts-node/register');
     });
 
+    it('should not register ts-node if it has already been registered', () => {
+      _.set(serverless, 'service.custom.webpack.webpackConfig', 'webpack.config.ts');
+      process[Symbol.for('ts-node.register.instance')] = 'foo';
+      new ServerlessWebpack(serverless, {});
+      delete process[Symbol.for('ts-node.register.instance')];
+      expect(Module._load).to.not.have.been.called;
+      expect(Module._load).to.not.have.been.calledWith('ts-node/register');
+    });
+
     it('should throw an error if config use TS but ts-node was not added as dependency', () => {
       moduleStub.throws();