Drew Storen has been transferred to the 60-day disabled list to make room for Gonzalez on the 40-man roster. Storen's stay on the DL is backdated to March 26, so this move will not affect the timetable for his return.
The addition of Gonzalez gives the Nats four left-handers in their bullpen, along with Sean Burnett, Tom Gorzelanny and Ross Detwiler.
"He's a very accomplished veteran left-handed relief pitcher," general manager Mike Rizzo said of Gonzalez. "We thought that it was a good fit for us at this time with some of the injuries that we have in the bullpen. He's a guy with great character that I've admired as a person for years. He's battle-tested, and he's a pretty good major league reliever."
The Nats signed Gonzalez to a minor league deal back on May 8. He spent a few weeks at the team's spring training facility in Viera, Fla., and then made just one appearance at Syracuse, going 1 1/3 perfect innings with two strikeouts.
"We had our scouts in the stands, and our staff there at Syracuse felt that he was ready to help us here in the big leagues," Rizzo said.
Gonzalez is coming back off offseason knee surgery, but the Nats believe the 34-year-old's arm is built up enough to allow him to be a factor immediately, even with the brief minor league stint.
"When he came to us, he was in great shape," Rizzo said. "He had been on a throwing program. We just took him, evaluated where he was in his process, and with (minor league pitching coordinator) Spin Williams in Florida, his assessment was that he was pretty close. We gave him three weeks down there to stretch his arm out, get his velocity back and get a feel for his breaking pitch.
"We activated him on a rehab assignment at Syracuse, and he threw extremely well. So, we thought that he was ready physically, and he was stretched out enough and his velocity was there that we could make the move."
Gonzalez has previously pitched for four teams over his nine-year big league career, posting a career line of 17-21 with a 2.94 ERA and 56 saves.
Perry went 1-0 with the Nats this season, with a 10.13 ERA in eight innings.