The move was announced Tuesday, shortly before the start of the NFL's free-agency period.
Caussin missed the past two seasons because of injuries. He was sidelined last season with a hip injury sustained early in training camp. Caussin missed the 2012 season because of a knee injury.
Caussin had five catches for 41 yards in six games, including two starts, with Buffalo in 2011 after being promoted off the team's practice squad.
He broke into the NFL with Jacksonville in 2010 as an undrafted free agent, but did not play a game with the Jaguars.
The Bills have a need at tight end, with returning starter Scott Chandler becoming a free agent.
AP NFL website: www.pro32.ap.org