A:AnswerThank you for your inquiry about one of our products. To answer your question, yes, they need to replace both switches since Geeni 3 way switch are designed to work together. For more details, please call us at +1 (888) 232-3143 or send us an email at [email protected]. You may also visit our support website support.mygeeni.com for live chat support. We are available from Mon-Sun from 10:00 AM to 7:00 PM EST.