The new deal for the Washington Wizard point guard will see him join the ranks of NBA players on its books.
Arenas won the 2002-03 NBA Most Improved Player award.
Said Kevin Wulff, director of sports marketing for adidas America: “Arenas is an exciting young player that will have a great impact on the game, our basketball business and our brand.
"We are impressed by his leadership and talent on the court and his personality off the court. We are confident that Arenas will help adidas continue its strong momentum in basketball."
Adidas currently has deals in place with more than 50 NBA players.
