Arrieta (2-2) was recalled from Class AAA Iowa prior to the game to make his seventh start of the season and second for the Cubs since being traded away by Baltimore. He allowed both St. Louis hits over seven innings, struck out seven and walked two.
James Russell and Blake Parker completed the shutout to snap the Cubs' four-game losing streak. It was only the second home win for Chicago in its last 13 attempts.
Nick Schierholtz singled in two runs during a three-run first and added a sacrifice fly in the fifth. Arrieta helped his own cause with a sixth-inning sacrifice fly.
The loss went to Jake Westbrook (7-8), who surrendered seven runs on eight hits with five walks in 6 2/3 innings.