Gonzalez (1-0) earned his first victory as a National since coming to Washington in a December trade. The left-hander baffled the Astros on two hits while walking two and striking out eight.
Tyler Clippard tossed a scoreless eighth and Brad Lidge survived a leadoff double by Jed Lowrie in the ninth to wrap up his second save and secure the victory for the NL East-leading Nats, who logged a second straight victory in its four-game set with Houston.
Adam LaRoche drove in the game's only run with a fourth-inning single.
Wandy Rodriguez (0-2) was the hard-luck loser, yielding only the one run on five hits over seven frames for the Astros. He didn't issue a walk and fanned three.