The Patriots star tight end was suspended one game for violating the NFL's rules on unnecessary roughness, the league announced Monday.
Gronkowski appealed the ban, though appointed arbitrator Derrick Brooks upheld the suspension Tuesday, league spokesman Michael Signora announced.
"Your actions were not incidental, could have been avoided and placed the opposing player at risk of serious injury," NFL VP of football operations Jon Rynyan wrote to Gronkowski in a statement released by the league. "The Competition Committee has clearly expressed its goal of 'eliminating flagrant hits that have no place in our game.' Those hits include the play you were involved in yesterday."