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 Baltimore Ravens custom jersey was signed in black by Brown and inscribed, "Hollywood" and "First Rd Pick." This jersey includes a JSA sticker and COA.