Samardzija (4-1) logged his third straight start without a loss, surrendering five hits and two walks while striking out seven, staking the Cubs to a victory in the first of a three-game set at Wrigley Field.
Chicago grabbed the lead on back-to-back solo homers by Ian Stewart and Bryan LaHair in the fourth inning and Geovany Soto added a two-run blast in the eighth.
Tommy Hanson (3-3) was touched for a pair of runs on five hits over six innings for Atlanta, which was coming off a three-game sweep of the Colorado Rockies.
Jason Heyward hit a bases-empty homer for the Braves' only run.
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