Project Ara allows users to buy a basic phone structure and add modules such as keyboard, battery or other sensors.
Motorola has partnered with Dutch designer Dave Hakkens, who has created Phonebloks, a modular phone idea, on the project.
Experts were unsure on how big a shake-up for the mobile phone industry the customisable handsets would represent.
In a blog post, Motorola said that it had been working on the project for more than a year.
“We want to do for hardware what the Android platform has done for software – create a vibrant, third-party developer ecosystem,” the firm wrote in a blog post.
“To give you the power to decide what your phone does, how it looks, where and what it’s made of, how much it costs and how long you’ll keep it.”
The project will consist of what Motorola is calling an endoskeleton, the frame that will hold all the modules in place.
“A module can be anything from a new application processor to a new display or keyboard, an extra battery, a pulse oximeter – or something not yet thought of,” the firm said.
Motorola plans to begin inviting developers to create modules in a few months time with a module developer’s kit launching soon afterwards.
Motorola came across the work of Dave Hakkens, the creator of Phonebloks, while developing the project and asked him to team up with them. Phonebloks has gained much interest in recent months.