The homer gave St. Louis a 2-0 lead with two outs in the top of the first.
Mark DeRosa, like Holliday, a trade-deadline acquisition, had three hits, including a solo homer.
Ryan Ludwick, Khalil Greene and Skip Schumaker each had one RBI, while Albert Pujols added three hits for the Cardinals, who have split their last four games.
Winner Chris Carpenter (11-3) surrendered four runs and nine hits in eight innings.
Closer Ryan Franklin earned his 25th save.
Pittsburgh's Garrett Jones and Ryan Duomit hit solo homers.
Delwyn Young had two hits and one RBI.
Steve Pearce had one RBI, while Duomit had two hits for the Pirates, who have lost six in a row.
The losing pitcher was reliever Jose Ascanio (0-2).
Copyright 2009 by United Press International.