Joe Nathan pitched a perfect ninth for his 35th save.
The AL West-leading Rangers took a quick lead over the last-place Astros. With two outs in the first, Ian Kinsler and Adrian Beltre doubled and Pierzynski hit an RBI single off Brett Oberholtzer (2-1).
Oberholtzer yielded seven hits and two runs with six strikeouts in 6 2-3 innings for his first loss in three major league starts.
The Houston hitters had no such luck with Darvish.
Darvish was strong from the start relying mostly on a four-seam fastball, sliders and a cutter against the Astros' inexperienced lineup.
"He doesn't just have control. This guy has command," Houston manager Bo Porter said. "He can throw every pitch the way he wants to throw it, even out of the strike zone. Which, when you have that kind of repertoire, you're going to be up against it."
He struck out the side in the first inning before getting two fly outs and a ground out in the second.
The 26-year-old righty fanned two each in the third and fourth innings, struck out the side in the fifth and the first batter of the sixth inning. His strikeout of Chris Carter to start the fifth was his 200th of the season, giving him a team record for fewest games (23) needed to reach the mark.
In the sixth, Darvish started walking off the mound after his close pitch to Villar. Pierzynski also began heading to the dugout, but Kulpa said it missed.
Pierzynski didn't like the call. After the walk, started yelling in Kulpa's face and was quickly tossed. Geovany Soto took over at catcher.
Darvish, a two-time MVP in Japan, flirted with perfection last Sept. 3, too, retiring the first 17 batters at Kansas City.
NOTES: Injured Texas DH Lance Berkman is getting Monday off and will DH for Double-A Frisco on Tuesday and Wednesday and will be re-evaluate him after that. ... Neftali Feliz, who was expected to throw Saturday for Round Rock but did not pitch as a precaution because of mild right arm triceps tendinitis, has been shut down. Feliz has been rehabbing from Tommy John surgery last year. ... Darvish set rookie franchise records for wins (16) and strikeouts (221) last season. He finished third in AL Rookie of the Year voting behind winner Mike Trout and Oakland outfielder Yoenis Cespedes.