To make room for Aardsma on the 40-man roster, the Mets moved Jeurys Familia to the 60-day disabled list. Aardsma will be available for Saturday's game against the Marlins.
"I had to really fight back and pitch to earn it," Aardsma said. "Last year was more of, OK, you came back. Now it's all right. I'm pitching and I made it. It feels great."
Aardsma, 31, made one appearance for the Yankees last season after returning from Tommy John surgery. He had a 1.13 ERA in eight relief appearances for Triple-A Las Vegas after beginning the season in the minors with the Marlins, following his release from the Yankees. Aardsma opted out with Miami after one month.
"I didn’t want to expect anything,” Aardsma said. “Just go down (to Triple-A), do my job and pitch and let the cards go the way they go and figure it out then."
Aardsma said the past few months were tough because he thought he had a "very good" spring training and would stick with the Yankees. He credits Las Vegas pitching coach Randy St. Claire with helping him refine his mechanics.
"There’s a couple of little changes here and there," Aardsma said. "Kind of where my feet were, my posture. I think it made a huge difference."
The Mets are set at closer with Bobby Parnell, but Aardsma could conceivably challenge to be the team's seventh- or eighth-inning reliever. The Mets have a collective bullpen ERA of 4.91, third-worst in the majors.
Aardsma is 13-15 with a 4.22 ERA in his career and has 69 saves, which came in 2009-10 when he served as the Mariners' closer.
"I only know what Wally (Backman) has been telling me and that is he's been throwing the ball great," Mets manager Terry Collins said. "His fastball has been very good, his split has been very good. He told me he's got swing-and-miss stuff, which is what you're looking for out of the bullpen."