The Cubs faithful were delighted as Jeff Baker chipped in with a two-run homer and Ryan Dempster (1-0) went 6 1/3 innings, allowing five runs on seven hits with four walks, to post the win for Chicago.
Derrek Lee contributed two hits with an RBI before but was taken out of the game in the fourth inning with right thumb inflammation.
Alfonso Soriano also collected a pair of hits in the Cubs' victory.
Ryan Braun smashed a three-run homer and drove in four runs as the Brewers dropped their third game in four tries. Doug Davis (0-1) was touched for six runs on seven hits over 3 1/3 innings.