He competed with Chris Long, Trey Flowers, and Frank Kearse throughout training camp for a backup defensive end role. On September 3, 2016, he was released by the Patriots as part of final roster cuts and was signed to the practice squad the next day. He was promoted to the active roster on October 15, 2016. On November 27, 2016, Grissom assisted on two tackles during a 22-17 victory against the New York Jets.
