Watson returned as the Patriots' primary starting tight end in 2005. On October 9, 2005, Watson scored his first NFL touchdown off of a 33-yard pass by quarterback Tom Brady as the Patriots defeated the Atlanta Falcons 31–28 in Week 5. In Week 11, he caught a season-high four passes for 66 receiving yards during a 24–17 victory against the New Orleans Saints. On December 11, 2005, Watson caught three passes for 35-yards before exiting in the fourth quarter of the Patriots' 35–7 victory at the Buffalo Bills after suffering a concussion. He remained inactive for their Week 15 victory against the Tampa Bay Buccaneers. Watson finished the 2005 season with 29 receptions, 441 receiving yards, and four touchdown receptions in 15 games and nine starts.