Club president Gary March made the announcement at Richmond's best and fairest presentation, where the players are vying to win the Jack Dyer medal for 2009.
It was widely anticipated Cousins would stay with the club he displayed strong form for after returning from a hamstring injury sustained in round one against Carlton.
The former West Coast Eagle played 15 games in his debut season at Tigerland, and is expected to feature strongly in Wednesday night's best and fairest voting.
