Molina went 4 for 5 with two RBIs and a run scored in the triumph Sunday at Busch Stadium. The performance helped the veteran catcher raise his season average from .233 to .314.
The Cardinals trailed 2-0 in the first inning before they scored six unanswered runs to claim the victory. St. Louis beat Cincinnati in three of four games to win the National League Central division series.
The Cardinals sit in second place in the division standings, three games behind the first-place Chicago Cubs. The Reds had just three hits in Sunday's setback and remain in third place in the National League Central.
Reds third baseman Eugenio Suarez pounced on a 3-1 first-inning fastball for a two-run homer to left center field to give Cincinnati an early lead before the Cardinals offense erupted.
Cardinals center fielder Harrison Bader tied the score with a two-run homer in the bottom of the second frame. That 409-foot blast off Reds starter Tyler Mahle traveled 105 mph and took 4.6 seconds to clear the center field fence, according to Statcast.
Molina then came to the plate in the bottom of the third inning and gave the Cardinals a 3-2 edge with an RBI single to center field. Molina returned to the batter's box in the bottom of the seventh inning and hit another RBI single to center field for a 4-2 lead.
Paul DeJong lined out in the next at-bat before Dylan Carlson settled in against Reds relief pitcher Nate Jones.
Jones picked up two quick strikes on Carlson before the Cardinals right fielder worked the count full. Carlson then hit Jones' seventh offering of the exchange -- an 87.5-mph slider -- deep to right center field for a two-run homer.
That 406-foot blast traveled 102 mph and left the field in 4.8 seconds.
Carlson went 2 for 4 with two RBIs and two runs scored in the win. Bader went 2 for 3 with an RBI and a run scored.
Cardinals starter Daniel Ponce de Leon allowed three hits and two runs in 4 2/3 innings. Mahle allowed five hits and three runs in three innings in his start for Cincinnati.