Phillips' RBI double in the sixth inning gave the Reds a lead, his two-RBI single in the eighth gave them breathing room and the Reds won a long and wild game, 12-9, in front of 22,991.
With both the Cardinals and Pirates losing on Saturday, the Reds now have a season-high 3 1/2-game lead in the NL Central. They haven't led the division by more than 2 1/2 games since winning it by five games in 2010.
"That was a big game for us to win, especially with the fact that the Cardinals lost, the Pirates lost," Reds manager Dusty Baker said. "We just got to keep grinding."
The Reds, who have won 11 of their past 14, certainly had to earn the victory after the Astros rallied from six runs down to grab a 9-8 lead after the fourth inning.
The bullpen, which had to get the final 17 outs after starter Mat Latos left in the third, mostly kept the Astros' bats at bay.
Sam LeCure pitched the fifth and sixth innings and picked up the victory, his first of the season. Jose Arredondo and Sean Marshall pitched scoreless innings to bridge the gap to Aroldis Chapman. He continued his dominant season, walking one but striking out three for his fifth save.
The Reds got the high-scoring affair started early. In the first inning, Zack Cozart scored on an RBI double from Drew Stubbs and Joey Votto took a 3-1 pitch from starter Wandy Rodriguez just over the right-field wall for his ninth homer of the season. The Reds led 3-0.
Latos gave up two in the first when Jose Altuve reached on a single and Jed Lowrie homered. The Reds responded with five in the top of the second, coming on a solo homer by Todd Frazier, a three-run homer from Stubbs and a RBI single from Votto.
The Astros fired back again, plating three runs in the third and four in the fourth to snag a 9-8 lead. Ryan Ludwick hit a solo homer to lead off the fifth, which tied the game until Phillips' sixth-inning double.
"We jumped off to a big lead, but around here, it always turns close sometime," Baker said. "My guys played with a lot of confidence. They didn't panic."
Phillips, who said he had a lot of energy Saturday, was pleased that he bounced back from going 0-for-3 in his first three at-bats.
"I got up twice and I put the beginning of the game behind me. I came up for the team," Phillips said. "It turned out to be a great day."
Phillips' late-innings heroics overshadowed a great day for Votto at the plate. He scored on Phillips' double in the sixth after getting a single with two outs. In the eighth, he was intentionally walked to load the bases for Phillips, who came through with the two-RBI single.
Votto had his fourth four-hit game of the season. He has a 20-game hitting streak at Minute Maid Park and his batting average over that span is .493.
"I've always felt pretty comfortable here," Votto said.
Astros manager Brad Mills said his team tried to change its approach to Votto mid-game.
"Right now, he's hitting away," Mills said.
Baker was satisfied with Saturday's outcome but said the Reds still need to figure out a way to get Latos on track. His 3 1/3-inning outing was his shortest of 2012. He gave up seven runs (four earned) and saw his ERA jump to 4.91 after posting a 3.26 ERA in five May starts.
"I thought he was over the hump," Baker said.
But because the Reds got to Rodriguez -- who pitched five innings, giving up nine runs (seven earned) and four homers -- Latos didn't factor into the decision.
"All that I know is that we got a 'W' out of it so that's all that matters," Latos said.
The game clocked in at 3 hours, 47 minutes, the second-longest game for the Reds this season.
"If we would've lost that game, I would've been [ticked], not because we lost the game, but because of how long we played the game and lost on top of it," Phillips said.