Chacin was 2-2 with one save and a 4.70 ERA in a career-high 44 relief appearances in two stints with the Astros last season. He joined the staff May 4 and his first outing May 7 was his first career relief appearance.
He did not allow a run in 11 of his final 12 appearances, and posted a 1.29 ERA over that stretch.
Houston had outrighted Chacin, 30, off the 40-man roster earlier in the offseason, but decided to invite him back. The Venezuelan lefty even helped at the plate. His first Major League hit was a home run on May 31 against the Nationals.
Chacin is the Astros' 12th non-roster invite and seventh pitcher they have committed to for 2011.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat This story was not subject to the approval of Major League Baseball or its clubs.