Cooper is best known for his Academy Award-nominated performance in the film "Silver Linings Playbook" and the "Hangover" comedy trilogy.
"Guardians" will also feature voice performances by Chris Pratt, Zoe Saldana and Dave Bautista.
Directed by James Gunn, the movie opens Aug. 1, 2014.
Notable deaths of 2014 [PHOTOS]
Jack Huston to star in remake of 'Ben-Hur'