In the deal made late Wednesday, the Phillies also got shortstop Eric Bruntlett, while sending outfielder Michael Bourn, reliever Geoff Geary, and minor league third baseman Mike Costanzo to the Astros.
Lidge was the key player in the first headline trade in baseball's off-season.
"He's got outstanding stuff and has been a guy who has pitched very well since he first came up," Phillies general manager Pat Gillick said on the team's Web site. "It's no secret we've been looking for pitching, and this certainly helps us there. Bruntlett's a guy who can play several positions, pinch-hit, run and help out in a lot of ways."
Lidge has 123 career saves with a 3.30 ERA.
Bruntlett, 29, is a career .250 hitter.
The speedy Bourn, 24, hit .277 in his first full season as a Phillies reserve with 18 stolen bases.