Allen was redshirted as a freshman in 2011. In 2012, he was the backup to Tyler Wilson. He appeared in five games and started one game after Wilson missed a game because of injury. He finished the season completing 21 of 49 passes for 186 yards with one touchdown and three interceptions. In 2013, Allen took over as the starting quarterback. He passed for 1,552 yards, completing 49.6 percent of his throws, and threw for 13 touchdowns and 10 interceptions for a team that finished 3-9 under first year head coachBret Bielema. As a junior in 2014, Allen had 2,285 passing yards, 20 touchdowns and five interceptions. He was the offensive MVP of the 2014 Texas Bowl, a 31-7 victory against the Texas Longhorns. Allen threw two touchdowns in the game, and Arkansas finished with a 7-6 record. During his senior year in 2015, Allen threw a then-school record six touchdown passes, and ran in the game winning 2 point conversion in a 53-52 overtime win over Ole Miss. He broke the record two weeks later with seven touchdowns in a 51-50 loss to Mississippi State. He also broke Arkansas' record for career passing touchdowns against Mississippi State. He finished the year with 3,440 passing yards, 30 touchdowns, and eight interceptions for a team that finished 8-5, and beat Kansas State in the 2016 Liberty Bowl, 45-23. Allen finished his career with 7,463 passing yards, 64 passing touchdowns, and 26 interceptions.
Statistics
Professional career
Jacksonville Jaguars
Allen was drafted by the Jacksonville Jaguars in the sixth round in the 2016 NFL Draft. On May 5, 2016, Allen signed a 4-year $2.48 million contract, which included a $147,687 signing bonus. Allen was the Jaguars third-string quarterback his rookie season behind Blake Bortles and Chad Henne. He was waived by the Jaguars on September 3, 2017, following final roster cuts for the 2017 season.
Los Angeles Rams
On September 4, 2017, Allen was claimed off waivers by the Los Angeles Rams. He was inactive for every game of the season as the Rams' third-string quarterback behind Jared Goff and Sean Mannion. He was placed on injured reserve on December 20, 2017. On September 18, 2018, Allen was waived by the Rams and was re-signed to the practice squad the next day. Allen signed a reserve/future contract with the Rams on February 7, 2019. On August 30, 2019, Allen was released as part of final roster cuts.
Denver Broncos
On September 1, 2019, Allen was claimed off waivers by the Denver Broncos. After an injury to starting quarterback Joe Flacco in week 8 of the 2019 season, Allen stepped in as the starting quarterback. Allen made his first start in Week 9 against the Cleveland Browns. In the game, Allen threw for 193 yards and two touchdowns in the 24–19 win.
Cincinnati Bengals
On August 1, 2020, Allen was signed by the Cincinnati Bengals.
His father, Bobby Allen, is the Razorbacks’ director of high school and NFL relations. He has a younger brother, Austin Allen, who became the starting quarterback for the Razorbacks after Brandon completed his college eligibility. Austin signed with the Tampa Bay Buccaneers as an undrafted free agent following the 2018 NFL Draft. Brandon Allen graduated in 2014 with a degree in recreation and sport management.
