Caussin, 27, was set to become a restricted free-agent at 4 p.m. Tuesday. The 6-foot-5, 252-pound tight end has spent the last two seasons on injured reserve.
In 2011, Caussin played six games for the Bills, catching five passes for 41 yards. He entered the league as an undrafted free agent in 2010.
Since Caussin was a restricted free agent, the Bills had the option to tender Caussin a contract worth at least $1.3 million. By re-signing Caussin instead of tendering him, the Bills likely brought him back at a reduced cost.
Caussin will compete for a backup tight end job in training camp.