Allen recorded just his second reception of the game, but that's all the wide receiver needed to surpass Gates.
The 33-year-old has spent 12 of his 13 years in the NFL as a member of the Chargers.
Originally selected in the third round of the 2013 NFL Draft, Allen is currently the only player on the Chargers who was around when the team was still in San Diego.
He now has 1,024 career receptions, 70 of which came from his time with the Chicago Bears in 2024, for 11,794 receiving yards and 70 touchdowns.
Allen broke the record with Gates in attendance, who said that there's nobody else he would want to break the record but Allen.
Los Angeles won the game 25-10 as they improved to 7-3 on the year.