Chief product officer Panos Panay said: "We designed Surface Duo for people who want to get more done with the device in their pocket.
"Our internal research shows that three out of four people report struggling to complete complex tasks while away from their computer. That's because smartphones with a single screen aren't designed for you to easily do multiple things at once.
"We know dual-screen devices not only help people complete complex tasks faster but also require less cognitive effort, making them universally preferred for productivity tasks."
Surface Duo is priced at $1399 and is available for pre-order in the US from today, ahead of its launch on 10 September.
The two screens are held together by a 360-degree hinge.
A dedicated Surface Duo for business website has also been set up by Microsoft.