Brown was called up to the majors for the first time on September 16, 2015, and made his major league debut on September 19.[4] He got his first major league hit in his third start, an RBI double off Tyson Ross of the San Diego Padres, on September 22, 2015.[5] Brown appeared in 13 games for the Giants, with 12 starts, batting .231 with 5 RBIs.
In 2016 Spring Training, Brown hit .324 (11-for-34) with nine RBIs in 17 games and was voted winner of the Barney Nugent Award, given to a player in his first big league camp whose performance best exemplifies the Giants spirit.[6] Brown was named to the Giants' 2016 opening day roster as the backup catcher.[7][8] On April 8, 2016, Brown hit his first major league home run, a game-tying two-run shot in the eighth inning off Chris Hatcher of the Los Angeles Dodgers that was the first Giants hit of the game.[9] On April 12, 2016, Brown hit two home runs playing against the Colorado Rockies, becoming the first Giant to hit home runs for his first three hits in a season since Kevin Mitchell in 1991.[10] He was outrighted to AAA on October 2, 2017.
On Saturday, June 9, 2018, Brown was released by the Giants after having played in only nine games in AAA for the Sacramento River Cats.[11]
On Sunday, June 10, 2018, Brown re-signed with the Giants to a minor-league contract.[12] He was released on September 28, 2018.