Upamecano's latest Instagram post, made April 1, received racist comments after the German club lost 3-0 to Manchester City in the first leg of the Champions League quarter-final.
“All of us at FC Bayern condemn racism in the strongest possible terms!" wrote Bayern Munich in a statement. "The entire club stands behind you, Upa!”
Fans and fellow players have since gone into the comment section to offer support to Upamecano following the racist responses.
"Head up champ," wrote Waldhof Mannheim right-back Niklas Wilson in a comment that now has more than 25,000 likes.
Upamecano, along with several of his team-mates, struggled against Manchester City and was already visibly dejected on the pitch before experiencing abuse.
Football continues to struggle to cut out racism - both on social media and in stadiums. Recently, Inter striker Romelu Lukaku said he faced racist taunts from Juventus supporters in the Coppa Italia.
"2023 and still the same problems," PSG star Kylian Mbappe wrote in French on his Instagram story after the Lukaku incident. "But we're not going to let it keep happening."