He played college football for the UCLA Bruins, earning second-team all-conference honors in the Pac-12 in 2020 and 2021.

Thompson-Robinson made his preseason debut in the 2023 Hall of Fame Game, where he replaced Browns' backup quarterback Kellen Mond.

[19] After a stellar preseason, Thompson-Robinson was named the backup quarterback behind Deshaun Watson, beating out Mond and Joshua Dobbs for the position with the latter being traded to the Arizona Cardinals.

[20] On October 1, Watson was ruled out in a game-time decision with a shoulder injury hours before the game against the Baltimore Ravens.

[22] He won his next start 13–10 over the Pittsburgh Steelers in Week 11, completing four of five passes on the final drive to set up a game-winning field goal.

[20] The following week against the Denver Broncos, Thompson-Robinson threw his first career touchdown pass, a two-yard score to tight end Harrison Bryant in the third quarter.

[23] He cleared concussion protocol ahead of Week 14 but was reverted to the backup role after the Browns announced Joe Flacco would be the team's starter the remainder of the season.

[24] In Week 16, Thompson-Robinson briefly appeared during garbage time against the Houston Texans and injured his hip.

He first appeared in a regular season game on October 20, after Deshaun Watson suffered an Achilles injury.

Thompson-Robinson completed 11 passes in 24 attempts for 82 yards and two interceptions in relief before leaving himself with a finger injury.

[26] He was replaced by Jameis Winston, who was named the starting quarterback for the Browns' next game; Thompson-Robinson's finger had recovered sufficiently for him to be the backup.

[28] The following week, the Browns announced that Thompson-Robinson would start their upcoming game against the Cincinnati Bengals.

[30] Thompson-Robinson also started Cleveland's next game against the Miami Dolphins, and completed 24 passes in 47 attempts for 170 yards, threw an interception, lost a fumble, and committed three intentional grounding penalties in a 20–3 loss.