By 1985, Cedeño was one of the Reds' five active members of the 2000-hit club, along with Pete Rose, Tony Pérez, Dave Concepción and Buddy Bell.
On August 29, 1985, he was traded for an outfielder named Mark Jackson to the St. Louis Cardinals, where he hit .434 with six home runs in 28 games, and arguably provided the necessary power for his new team to outpace the New York Mets to reach the playoffs. With only one month left in the season, Cedeño had the Cardinals' longest hitting streak during their 1985 season. He then played at first base to replace the injured Jack Clark in the final regular season games, and played in the outfield in the playoffs to help replace the injured Vince Coleman. Cedeno was granted free agency on November 12, 1985.