Pitcher Sam Freeman, who was on St. Louis' NLDS roster, was removed to make room for Pierzynski.
The Cardinals signed Pierzynski in July after he was designated for assignment and then released by the Boston Red Sox.
Pierzynski hit .251 with five home runs and 37 RBI in 102 games this season. The veteran has a lifetime .300 average in 30 career postseason games from his time with the Twins and White Sox, including five home runs. He has not appeared in a playoff game since 2008.
Freeman had a 2.61 ERA with 35 strikeouts in 38 innings in 2014. He appeared the Game 1 of the NLDS against the Los Angeles Dodgers, walking two batters and failing to record an out. The Cardinals won the series in four games.
Game 1 of the NLDS between St. Louis and the San Francisco Giants is Saturday night.
- Molly Geary