Though there have been no recent leaks about the phone, Microsoft announced last October that it would launch an Android smartphone this year.
The company has used the Surface brand for its tablets and some laptops, but all have been Windows-based.
The Surface Duo will be sold only in the US initially for US$1399 (A$1953). The specs can be viewed here.
Panos Panay, chief product officer, Windows + Devices, said in a blog post: "Surface Duo brings together the power of Microsoft 365 experiences and the full ecosystem of Android mobile apps into one device, with two screens that you can take anywhere.
"We have worked to optimise apps including Office, Outlook, Teams, Edge, OneNote, OneDrive, Microsoft To Do and more for two screens, while continuing to extend Windows to add more value to people also using Android phones."
He said Surface Duo was available for pre-order from Wednesday through MicrosoftStore.com, AT&T and BestBuy. It will be available in store and online from 10 September. The device will work on the AT&T, T-Mobile and Verizon Wireless networks.