The man, who police said was an off-duty prison guard, was shot outside the Palmeiras stadium in Sao Paulo, where thousands of fans gathered to watch the match on big screens.
“Some clashes erupted between fans, causing riots and a man was shot dead,” the military police said in a statement.
Riot police used tear gas and rubber bullets to disperse the crowd, and the statement said one man was arrested.
Police said the images would be analyzed to identify others involved in the riots, while police continued to patrol the area to prevent any new disturbances.
Chelsea beat Libertadores Cup champion Palmeiras 2-1 after extra time in the match that was held in Abu Dhabi.
Palmeiras was seeking to win the annual championship for the first time and join his rivals in the state Corinthians, Santos and Sao Paulo, who have all won the title of the championship held between the continental champions.