Houston gets Wolf, who went 6-10 with a 4.74 ERA in 21 starts for San Diego, for the rest of the season, after which he will be a free agent. He signed a one-year deal with the Padres in December for $4.75 million.
General Manager Ed Wade said with performance-based bonus potential, the veteran could earn more than $3.5 million with the Astros.
"Obviously, we felt that if we had an opportunity to upgrade our starting rotation between now and the [July 31] trade deadline, it made sense for us to try to do that," Wade said. "We tried to sign him as a free agent this past offseason and lost out to the allure of the West Coast. We're fortunate to have him at this point in time. I think he's going to fit very well into the starting rotation, and it gives us two lefties in the rotation and gives us another guy who's a great competitor."
Wade said Wolf will report to the club on Friday in Milwaukee for bullpen practice, and he expects the 31-year-old to start Sunday against the Brewers.
Wade is familiar with Wolf, having signed him when Wade was with the Phillies.
Wolf has had some struggles in the past couple of seasons both with performance and health, but after talking to Wolf's doctors, Wade is confident the veteran is healthy.
"We had the discussion during the offseason with regards to how healthy he was," Wade said. "We thought he was healthy enough for us to offer about $7 million for him to come pitch for us, but unfortunately, we couldn't get the deal done. From the trainer discussions that we had today, he's 100 percent healthy. He struggled at times over the course of this season, but again, he's a competitor. Hopefully, we'll provide him enough support to where he can get deep enough into the games and help us win."
Wolf pitched for the Phillies from 1999 to 2006 before signing a one-year contract with the Dodgers for the 2007 season. He is 84-76 overall with a 4.30 career ERA.
The transaction means Wade still feels the Astros have a shot at the postseason. Entering Tuesday, Houston was second-to-last in the Central Division, 12 games back of the Cubs.
Wade sees potential to keep Wolf beyond this season.
"I'm going to remain optimistic that we're going to play solid," Wade said. "The Wolf trade is a case where we have a chance to improve both short term and long term because it is a one-year deal, he is a free agent at the end of the year, and he's pitching for his next contract. He hasn't given any indication that he doesn't want to continue to play. ... This gives us a short-term help that we need; it gives us an opportunity to get our foot in the door with Randy if he pitches well enough that we want to extend the contract."
Krysten Oliphant is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.