Larry Walker hit a pair and Albert Pujols, Jim Edmonds and light-hitting catcher Pat Matheny each hit one to back starting pitcher Woody Williams, who surrendered two runs on eight hits in six innings with one walk and two strikeouts.
With the five homers, the high-scoring Cardinals tied a major league record for a playoff game.
St. Louis broke the game open early by scoring five runs off Dodgers starter Odalis Perez in the third inning. Against three St. Louis relievers, the Dodgers only hit one ball out of the infield, a solo home run by catcher Tom Wilson in the ninth inning.
Game 2 of the series is to be played Thursday night in St. Louis.