Watson entered the league after scoring a 48 on his Wonderlic Test. That is tied for third highest score ever in the NFL. He was drafted by the New England Patriots 32nd overall in the 2004 NFL draft. He was on the injured list for almost his entire rookie season for the Patriots, playing in only one game. Watson received a Super Bowl ring following the Patriots' win over the Eagles in Super Bowl XXXIX.
He continued to battle injuries throughout his stint in New England, starting just 47 games in six seasons with the team. He nabbed a career-best six touchdown passes in the Patriots' undefeated 2007 campaign, third best on the team.
On March 12, 2010, Watson signed a three-year deal with the Cleveland Browns, reuniting him with former Patriots assistant coach, Eric Mangini. In the 2010 season, Watson led the Browns in receptions, receiving yards, and receiving touchdowns (tied with Brian Robiskie).
On March 18, 2013, Watson agreed to terms on a three-year contract with the New Orleans Saints. In 2015 he was elected as one of the offensive team captains (along with Drew Brees and Zach Strief). On October 15, 2015 he had one of the best games of his career, catching 10 passes for 127 yards and a touchdown as the Saints beat Atlanta in a nationally televised Thursday Night Football game.
^Gregg Rosenthal, "Saints knock out Falcons from ranks of undefeated", NFL.com, October 16, 2015 ("It should forever be remembered as The Ben Watson Game, as the 12-year veteran did his best Jimmy Graham impression with 10 catches and 127 yards and a touchdown. It was cool to watch one of the league's longtime good guys put up a random career game in his 12th season.")