Patriots quarterback Tom Brady threw for 259 yards and two touchdowns to help Belichick earn the milestone victory. With win No. 300, which includes postseason play, Belichick trails only Don Shula (347) and George Halas (324) on the NFL's all-time list.
"It's a great privilege to coach this team and to coach the guys that I've coached throughout my career," Belichick told reporters Sunday. "Fortunately I didn't play in those games. That's a good thing for us. But I've had a lot of good players, a lot of great players, and they're the ones who win the games."
Belichick's monumental win came against his former team in the Browns. He was 39 years old when he coached Cleveland to a win over the Patriots in 1991. It marked his first victory as an NFL head coach.
"It's always good to win," Belichick said. "It's good to beat Cleveland. It's good to beat anybody. It's a tough league to win in. I'm proud of what the guys did, proud of what the team accomplished today, but we've got bigger goals ahead."
Browns quarterback Baker Mayfield continued to struggle, completing 20-of-31 passes for 194 yards, one touchdown and one interception.
The Patriots will play the Baltimore Ravens next week, while the Browns will travel to Denver for a matchup against the Broncos.