Brown was selected 25th overall by the Baltimore Ravens in the first round of the 2019 NFL Draft. He made his regular season debut in a game against the Miami Dolphins on September 8, 2019, recording 4 receptions, 147 receiving yards and 2 touchdowns despite playing only 14 snaps. Brown became the first player in NFL history to score 2 touchdowns of 40 yards or more in his first game. In week 12 against the Los Angeles Rams on Monday Night Football, Brown caught 5 passes for 42 yards and 2 touchdowns in the 45–6 win. On December 12, 2019, Brown caught a touchdown from Jackson in a 42–21 win over the New York Jets on Thursday Night Football, which tied the Ravens franchise record for most receiving touchdowns by a rookie with 7. Brown finished 2019 as the Ravens' 2nd leading receiver behind tight end Mark Andrews.
This Oklahoma mini helmet was signed in white by Brown and includes a JSA sticker and COA.