Police said the man, whose identity was not revealed, was an innocent bystander as rival fans clashed in the entrance of the Sao Miguel train station in Sao Paulo's eastern suburbs on Sunday, Xinhua news agency reported.
"A man who was not a fan was shot in the heart and died," police officer Luiz Gonzaga told the Folha de S.Paulo newspaper.
In another incident on Sunday, 25 people were reportedly injured during clashes between fans of the same teams.
Corinthians and Palmeiras are among Brazil's most successful clubs, having won 14 Brazilian top flight titles between them since 1959.
Palmeiras won Sunday's Sao Paulo state league match 1-0 at Allianz Parque. (IANS)