Allen was selected by the
Los Angeles Rams in the fifth round, 175th overall, of the
2023 NFL draft. He played in 15 of 17 games during the regular season. In Week 14, Allen caught a season-high four passes for 50 yards, including a 7-yard pass from quarterback
Matthew Stafford for his first career NFL touchdown in the Rams' 37–31 overtime loss to the
Baltimore Ravens. Against the
San Francisco 49ers in Week 18, Allen made his first professional start, catching four passes for 25 yards in the Rams' 21–20 victory. In an
NFC Wild Card Game at Detroit, Allen caught two passes for 28 yards in the Rams' 24–23 loss to the Lions. In 2024, Allen played in 15 out of 17 games, and made the first out of five consecutive starts in Week 10, catching five passes for 34 yards in the Rams' 23-15 loss to the
Miami Dolphins. In L.A.'s 27-9 victory over the
Minnesota Vikings in an NFC Wild Card Game, Allen caught one pass for a 13-yard touchdown. Allen played in all 17 regular season games in
2025 and started in five (including the team's final four games), setting new personal single season highs in receptions (24), yardage (208) and touchdowns (three) as he helped the Rams reach the playoffs for the third consecutive season. Allen played a career-high number of snaps as the Rams made a significant increase in their usage of multi-tight end sets, notably having an irregular increase in their usage of 13 personnel, a personnel grouping of 3 tight ends and 1 running back, rather than the more commonly used 12 personnel grouping, which consists of 2 tight ends and 1 running back, with Allen being a part of a tight end unit that also featured
Tyler Higbee,
Colby Parkinson, and
Terrance Ferguson. Allen was also the Rams' unofficial main
fullback during the 2025 season and led all Rams tight ends aligned in snaps in the backfield. Allen recorded 24 receptions for 208 yards and 3 touchdowns during the 2025 season. ==Career statistics==