The tight end out of Washington was the 38th overall selection after winning last season's John Mackey Award, presented annually to the nation's top college tight end.
Seferian-Jenkins finished his college career with 146 receptions for 1,840 yards and 21 touchdowns - all Washington records for a tight end.
The signing Thursday means the Bucs have their entire draft class under contract.
Meanwhile, the team also signed free- agent wide receiver David Gettis. He was a sixth-round draft pick of the Carolina Panthers in 2010.