Under the Collective Bargaining Agreement, the Angels would have had to pay $100,000 to keep Isringhausen, who signed to a Minor League contract at the start of Spring Training, on the roster past 9 a.m. PT.
Angels general manager Jerry Dipoto informed the 39-year-old on Thursday night that the club would be keeping him on the roster. Isringhausen signed a big league contract on Friday morning.
"I'm thankful for the opportunity," Isringhausen said. "I'm going to give them everything I've got."
Isringhausen, who has 300 saves in his 15 Major League seasons, pitched back-to-back clean innings on Wednesday and Thursday in hopes of showcasing to the Angels that he belonged on the club. He said he would have retired if the Angels cut him.
Alden Gonzalez is a reporter for MLB.com. Read his columns and his blog, Gonzo and "The Show", and follow him on Twitter @Alden_Gonzalez. This story was not subject to the approval of Major League Baseball or its clubs.