Brewers 8, Cubs 7 (13)
Corey Hart hit a game-tying two-run homer in the ninth inning and added the decisive RBI single in the 13th to lift host Milwaukee.
Lendy Castillo (0-1), Chicago's eighth pitcher, set the winning rally in motion by hitting Rickie Weeks and Ryan Braun to open the inning.
Aramis Ramirez followed with a single into right field to load the bases for Hart, who chopped a grounded through an open hole at second base after the Cubs moved three infielders to the left of second base.
Hart broke a 12-game homerless streak with a two-run blast in the bottom of the ninth to send the game into extra innings for the Brewers, who beat Chicago for the ninth straight time at Miller Park.
David DeJesus clubbed his first career pinch-hit grand slam and drove in five runs for Chicago, which fell one game behind the Brewers for last place in the National League Central.
Jonathan Lucroy added a pinch-hit three-run double in the bottom of the seventh inning to put Milwaukee ahead after the Cubs had taken a 4-1 lead in the top of the frame.
The Cubs went ahead with a three-run ninth. DeJesus tied it with an RBI triple off Brewers closer John Axford, ending his streak of consecutive saves at 49 games. DeJesus scored on a wild pitch and Alfonso Soriano made it 7-5 with an RBI single.
Cubs closer Rafael Dolis couldn't preserve the lead, suffering his second blown save in five chances.
Vinnie Chulk (1-0), the eighth pitcher for the Brewers, worked two innings for the victory.
GAME NOTEBOOK: Cubs reliever Carlos Marmol left the game with a hamstring injury in the seventh. ... Lucroy's pinch-hit double extended his hitting streak to eight games. ... DeJesus hit his first homer with the Cubs and belted his his first career pinch-hit home run. He had only four RBIs entering the game. ... Brewers P Kameron Loe had a string of seven consecutive scoreless appearances snapped. It was his first homer allowed since April 8 against St. Louis. ... Cubs 1B Bryan LaHair drew an intentional walk in the 13th inning to extend his streak of reaching base to 28 straight games.