Domingo Santana singled in Eric Thames to put Milwaukee ahead 2-1 in the ninth inning, but Tommy Pham scored from second on a pair of wild pitches by Jacob Barnes to tie it in the bottom of the inning.
After Orlando Arcia singled in a run in the top of the 10th, Greg Garcia made it 3-3 with his own RBI single a half-inning later.
Eric Thames homered in the first inning for the Brewers.
St. Louis starter Carlos Martinez allowed a run and six hits over six innings. He stuck out four and walked two.
Brent Suter held the Cardinals to a run and four hits over 5 1/3 innings.
Brewers: C Manny Pina was removed in the seventh inning with tightness in his right calf. … OF Lorenzo Cain is listed as day-to-day after bruising his Achilles tendon in a first base collision with Jose Martinez on Monday.
Cardinals: Martinez was also held out of the starting lineup due to the collision with Cain. He is day-to-day.
Milwaukee RHP Junior Guerra will make his first start of the season against St. Louis RHP Adam Wainwright (0-1, 7.36) in the final game of the three-game series Wednesday. Wainwright gave up three runs in 3 2/3 innings of a 3-1 loss to Arizona on Thursday.