Brazilian champions Fluminense squandered a 2-1 lead and lost 3-2 to Botafogo while Ronaldinho scored his first goal for Flamengo in other matches in Brazil's state championships.
Corinthians' victory in the Sao Paulo derby came after three days of violent protests following Wednesday's upset by Colombia's Deportes Tolima in the preliminary round of South America's elite club competition.
Right back Alessandro scored the goal that may begin to heal Corinthians' wounds seven minutes from the end of the Paulista state championship match.
"Because of what we were going through and the importance of a victory, this was without doubt the best match of my career," the 26-year-old keeper told reporters.
"It's still not a happy time but this is a new start for Corinthians."
Palmeiras, trained by former Brazil and Portugal coach Luiz Felipe Scolari, were the better team but were foiled time and again by Julio Sergio's inspired goalkeeping.
Corinthians were without rested former Brazil players Ronaldo, the team's captain, and Roberto Carlos whom fans hold mainly responsible for the Libertadores Cup debacle.
The first half ended with both sides down to 10 men after Botafogo's Marcelo Mattos and Fluminense's Colombian midfielder Edwin Valencia were sent off for violent fouls.
