The Get Lucky star's debut range with the brand is set to debut this summer, and will be created with his eco-friendly Bionic Yarn.
This material is made using plastic debris from the sea through international collective The Vortex Project.
Williams said: "Working with an iconic brand like Adidas is such an incredible opportunity. From the classic tracksuit, to growing up in Virginia wearing Stan Smiths, Adidas has been a staple in my life. Their pieces are timeless. This is an exciting partnership for both me and for Bionic Yarn."
The musician is also currently working on a collection for Uniqlo, while Adidas recently launched a line at high-street favourite Topshop.
Dirk Schoenberger from Adidas commented: "I am truly thrilled to work with Pharrell.
"He is a pop-culture icon who never fails to inspire, not just through his musical talent and craft, but through his many other interests. He is the perfect fit for the multi-faceted company that is Adidas."