The five-time Super Bowl champion and three-time NFL MVP walked onto the field outside Gillette Stadium in Foxborough, Mass. Fans stood up in the bleachers while singing the song as Brady entered the facility.
The Patriots also served a giant birthday cake for Brady, in the shape of his No. 12. The cake had white frosting with red, white and blue filling. There were also inflatable depictions of the superstar gunslinger, G.O.A.T. signs, No. 12 signs and a giant birthday card for fans to sign.
Patriots coach Bill Belichick was mum on what he got for Brady's birthday, but he did give the future Hall of Famer a compliment.
"He has had a tremendous career," Belichick told reporters. "He has had a spectacular career. He still plays at a very high level."
Last year, the Patriots had actual goats at training camp for Brady, a metaphor for his "greatest of all time" moniker. Fans also sang to the quarterback last year.
The Patriots begin the regular season at 1 p.m. Sept. 9 against the Houston Texans at Gillette Stadium. Brady led the league with 581 passing attempts and 4,577 yards last season en route to the 2017 NFL MVP award. He has been ranked the No. 1 player in the NFL Top 100 for back-to-back seasons.