The man, who police said was an off-duty prison guard, was shot outside Palmeiras' stadium in Sao Paulo, where thousands of fans had gathered to watch the match on big screens.
"There were some outbreaks of fighting among fans, which unleashed a riot and a man was shot," a military police statement said.
Riot police used teargas and rubber bullets to disperse the crowds. One man was arrested, the statement said. Images will be analyzed to identify others involved in the riots, police said. Police continued to patrol the area to prevent any new disturbances.
Chelsea beat the Copa Libertadores champions 2-1 after extra time in the game in Abu Dhabi. Palmeiras were aiming to win the annual tournament for the first time and join state rivals Corinthians, Santo sand Sao Paulo, all of whom have won the trophy played between the top club sides in the world.