Maholm (9-6), who had spent his entire seven-season career with the Pirates before signing with the Cubs as a free agent in January, yielded four hits and struck out seven with one walk in his second appearance against his former team.
The left-hander registered a no-decision in a 3-2 Cubs loss to Pittsburgh May 26.
Bucs starter James McDonald (10-4) absorbed the loss, giving up five runs on five hits in a six-inning effort.
Garrett Jones homered to provide the only run for the second-place Pirates, who came into the contest trailing National League Central-leading Cincinnati by 1 1/2 games.
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