Pirates 3, Cubs 2: Rookie Matt Hague was hit by a pitch with the bases loaded in the ninth inning as Pittsburgh handed Chicago its 11th straight loss.
Pedro Alvarez and Neil Walker drove in a run apiece for the Pirates, who go for the sweep of the three-game series Sunday.
Jose Tabata hit a leadoff single off Rafael Dolis (2-4) and Josh Harrison walked before the Cubs reliever retired two batters. Walker drew a free pass to load the bases for Hague, who was plunked by a 2-2 offering to drive in Tabata with the winning run.
Joel Hanrahan (2-0) struck out two in a perfect top of the ninth to notch the win.
Pittsburgh jumped out to a 2-0 lead in the third as Alvarez delivered an RBI single and Walker followed with a sacrifice fly. But Chicago pulled even on a two-out solo homer by Alfonso Soriano in the fourth and an RBI triple by Starlin Castro an inning later.
The Cubs nearly went ahead in the seventh, but Blake Lalli was thrown out at the plate trying to score from first on pinch hitter Adrian Cardenas' double.
Chicago starter Paul Maholm lasted five innings in his first start against his former team. The left-hander allowed two runs and five hits.
The Cubs' losing streak is their longest since they began the 1997 season with 14 straight defeats.
GAME NOTEBOOK: Cubs 3B Ian Stewart was back in the lineup after being scratched on Friday due to a sore left wrist. Stewart went 0-for-3 with a walk. ... Chicago RH Carlos Marmol is scheduled to make his second rehab appearance with Triple-A Iowa on Sunday. The former closer, who is on the 15-day disabled list with a strained right hamstring, tossed one scoreless inning for Iowa on Friday, allowing one hit and one walk while striking out a batter. ... Deuces were wild for Pirates CF Andrew McCutchen as he recorded two hits, stole two bases and walked twice.