Pujols, who narrowly missed a fourth homer when he flied deep to left in the seventh inning, raised his season home run total to 42, marking the fourth consecutive year he has reached that figure.
The trifecta came on a day when children with afflicted with Down's syndrome were featured on the field before the game, standing next to Cardinals players before the national anthem. Pujols, who has a daughter with Down's, generally has had big offensive days on what are called "Buddy Walk" days.
Since being installed as spokesperson for the program in 2002, Pujols has hit five homers and driven in nine runs while batting .450 in games played on those special days.
"He always has extra incentive (on those days)," manager Tony La Russa said. "He's amazing."
Against Pittsburgh, Pujols has been little short of destructive in his career, hitting 32 homers and driving in 91 runs (five on Sunday) in 339 at-bats.
With rookie Anthony Reyes hurling 6 1/3 scoreless innings, the Cardinals finished up a 7-2 homestand against the Cubs, Marlins and Pirates.
"That's about as good as we can do," La Russa said. "Winning three series like that is very important. Well done."
REPLAY: Right-hander Anthony Reyes, called up for the third time from Triple-A Memphis, fanned a career-high nine and gave up only four hits as he blanked Pittsburgh for 6 1/3 innings Sunday in a 6-3 win that gave the Cardinals the series victory, two games to one.
Albert Pujols, who had hit only .211 over his previous 10 games, accounted for his second three-homer day of the season by connecting in the first, third and fifth off Pittsburgh's Ian Snell. Pujols drove in five runs.
--RHP Anthony Reyes posted his fifth victory and third in his last four decisions. He next will pitch at Arizona on Friday night. Though he wasn't activated until Sunday, Reyes would be eligible for the playoff roster because the Cardinals have several players who will be on the disabled list for the remainder of the season. Reyes fanned the side in the first inning, the first time a Cardinals pitcher had achieved that feat this season.
--The 12 strikeouts by Cardinals pitchers represented the second most this season. They fanned 16 on June 13 in Pittsburgh.
--1B Albert Pujols scored three runs Sunday, giving him 100 for the season, the sixth consecutive season he has done that. He already has driven in 100 or more runs for six straight seasons.
--C Yadier Molina ended an 0-for-13 dive with a single and a double.
--Cardinals pitchers posted a 3.22 ERA during the nine games on the homestand. The starters were at 2.95, including LHP Mark Mulder's five-run outing in 1 2/3 innings.
--RHP Brad Thompson and OF John Rodriguez were recalled from Triple-A Memphis when rosters expanded.
BY THE NUMBERS: 10 -- Number of series sweeps the Cardinals have suffered this season. It's the most since 1997, when they were swept 11 times.
QUOTE TO NOTE: "It could be a week, it could be 10 days or it could be two months." -- CF Jim Edmonds' timetable for returning from post-concussion syndrome.