Marcum (2-1) was perfect through four and kept the Pirates off-balance with his changeup, allowing only four singles with four strikeouts and a walk. Acquired in an offseason trade with Toronto to bolster Milwaukee's rotation, Marcum lowered his ERA to 2.55 through three starts.
"Very pleased," Brewers manager Ron Roenicke said. "He moved his ball around well, changed speeds, he's cutting it and he's sinking it, and he knows when to throw the pitches is the thing. That's what I saw from him last year. That was the same guy."
The Pirates have lost four of five. Correia (2-1) took a no-hitter into the sixth, but his outing quickly unraveled from there.
On a night when the Penguins opened the NHL playoffs across town, the announced crowd was 8,755 -- but only about 4,000 actually showed up. Early on, those who did thought they might be witnesses to history with both starters working on no-hitters by the midway point.
"Anytime you're in a pitching duel it's always fun," Marcum said. "Tonight was one of those nights. I think having a couple days off kind of screwed [the hitter's] timing up on both teams. It was just one of those days when you've got to throw strikes, keep the ball down and let them try to get themselves out, and we were able to do that for the most part."
It took less than an hour to get through the first 4½ innings. The only two baserunners to that point were Rickie Weeks, whom Correia walked leading off the game, and Casey McGehee, who drew a walk off Correia in the fifth.
Correia and Marcum combined to retire 24 consecutive batters in between.
"Shaun pitched a great game," Fielder said. "I was just glad we were finally able to get him some runs."
Correia's no-hitter was broken up by Jonathan Lucroy's double to lead off the sixth. Marcum followed by attempting to sacrifice him to third but ended up reaching and was credited with a single.
With one out, Carlos Gomez's high sacrifice fly down the right-field line was deep enough to score Lucroy, who was making his season debut after being on the disabled list with a broken finger.
Ryan Braun followed with a single, setting up Fielder's homer on an 0-1 pitch into the bullpen in left-center.
"I was pitching well, and then I had one bad inning," Correia said. "But a lot of times, all it takes is one bad inning to lose a game."
The reigning NL player of the week, Fielder has at least a hit and an RBI in each of his past six games, totaling three home runs and 14 RBIs in that time.
Traditionally a pull hitter, none of the left-handed hitting first baseman's three home runs this season have gone to right field. Twenty-two of his 194 career homers have come against the Pirates, most of any opponent.
"When he's driving the ball the other way like that, that's bad news for the opposing pitchers because there's really not much they can do with him," Roenicke said."
Fielder has 10 RBIs in his past four games.
Yuniesky Betancourt added an RBI double in the seventh -- ending Correia's night not long after his bid for a no-hitter ended -- and Betancourt would score on a Marcum groundout.
Correia's final stat line belied his impressive first five innings: Six-plus innings, six runs -- four earned -- five hits, two walks and a strikeout.
Pittsburgh leadoff hitter Jose Tabata failed to have a hit for the first time in 11 games this season.
The Pirates (5-6), who haven't had a winning season since 1992, fell under .500 for the first time this season. Last season, they entered an April home series against the Brewers at 7-5 but were swept and outscored 36-1 and never were at .500 again.
"All I'm looking at is how we are executing and if we are getting better," Pirates manager Clint Hurdle said. "Tonight we didn't execute very well and we lost. For the most part, we've executed pretty well this season but this time we didn't."
After the game, the Pirates reinstated C Chris Snyder from the disabled list and optioned C Jason Jaramillo to Triple-A. ... Milwaukee is 47-17 vs. Pittsburgh since 2007, the best winning percentage for any team against a divisional opponent. ... Brewers manager Ron Roenicke said RHP Yovani Gallardo will start on Saturday and RHP Marco Estrada on Sunday.