The 2004 season was Edmonds' best season. He hit .301, had a .643 slugging percentage, 42 HRs, and 111 RBI; all but batting average were career highs. As a result, he earned a Silver Slugger Award, a Gold Glove Award, and was fifth in the voting for the Most Valuable Player Award.
A defining moment of Edmonds' career came in the 2004 National League Championship Series, in which Edmonds hit an extra-inning home run to win Game 6. In Game 7, Edmonds made a spectacular defensive play in center, helping the Cardinals win the pennant.
During a Chicago Cubs-Cardinals game at Wrigley Field on July 19, 2004, pitcher Carlos Zambrano was ejected from the game for throwing at Edmonds. Zambrano screamed at Edmonds as he rounded the bases on a home run, earning Zambrano a five-game suspension.