Corinthians, who reached the final of South America's elite competition for the first time when they eliminated holders Santos on Wednesday, had only taken one point from their first five matches of the domestic championship.
The victory over Luiz Felipe Scolari's side in a Sao Paulo derby lifted Corinthians off the bottom of the standings with four points from six matches, two more than Palmeiras and Goianiense.
Striker Romarinho scored once in each half for Corinthians after Mazinho had put Palmeiras ahead in the fourth minute.
Corinthians were captained by former Portugal striker Liedson who might have scored a brilliant goal had his bicycle kick not hit the woodwork and run along the goal-line before going out of play.
Their first team meet six-times South American champions Boca Juniors of Argentina in the Libertadores final, with the first leg at La Bombonera in Buenos Aires on Wednesday.
Santos, with a full team in the domestic championship for the first time after failing to progress from the Libertadores Cup semi-finals, were held 2-2 at home by Coritiba.
Brazil striker Neymar put Santos 2-1 up at a free-kick in the 70th minute at the Vila Belmiro but Lincoln equalised four minutes later with a penalty.
Cruzeiro lead the standings with 14 points after a 3-1 away win over Vasco da Gama in a top-of-the-table clash in Rio de Janeiro on Saturday.
Their Belo Horizonte city arch-rivals Atletico Mineiro, equal second on 13 points with Vasco, crushed promoted Nautico 5-1 with their new captain Ronaldinho scoring his first goal for them from a controversial penalty.
The score was 1-1 when Mineiro's former Everton and Manchester City striker Jo went down in the box and Ronaldinho put them 2-1 up from the spot, opening the floodgates.
