Depending on which device you are using, there may be an option for you to transfer your chats.
Here is a step-by-step guide on transferring your WhatsApp chats from your old phone to your new phone:
Learn more about transferring your chats on: Android | iPhone | Windows Phone | Nokia S60| BlackBerry 10
Nokia S40 and BlackBerry devices cannot transfer chat history at this time.
If you are trying to recover your deleted chats, read this article.
Note: If you're using a different phone number on your new phone, you won't be able to transfer your chats.
Cheers,
WhatsApp Support Team