The Astros raced to a 3-0 first-inning lead, scoring two runs from the first four pitches from Phillies starter Zach Wheeler, before Alex Bregman's fifth-inning two-run blast shored up a 5-0 lead at Minute Maid Park.
The Phillies had rallied from that deficit on Friday but could not replicate that, despite plating runs in the seventh and ninth innings. Kyle Schwarber thought he had pulled it back to 5-3 with an eighth-inning two-run blast but that was called a foul after a replay review.
Framber Valdez was heroic, sending down 104 pitches before being retired in the seventh inning with nine strikeouts having allowed only four hits, three walks and one earned run.
Jose Altuve's lead-off double from the first pitch was followed by Jeremy Pena's left-field line drive from the second pitch to score the second baseman. Altuve put aside his postseason struggles with three hits for the game.
Two pitches later Pena scored when Yordan Alvarez's left-field shot sailed over Schwarber's head. Alvarez added the third in the inning from an error by shortstop Edmundo Sosa.
Wheeler corrected his early issues, allowing only two singles from 14 batters until Bregman's fifth-inning blast, his third of the postseason.
Nick Castellanos scored from Jean Segura's seventh-inning sacrifice fly, before Schwarber came close to halving the deficit twice, with his two-run blast overturned, followed by a right-field shot that was caught inches short by Kyle Tucker.