Wolf, who is nearly 19 months removed from Tommy John surgery, is expected to move into the Marlins' rotation. Prior to Wednesday, he had not pitched in the major leagues since he ended the 2012 season with the Baltimore Orioles.
Wolf, who turns 38 in August, had been pitching for the Arizona Diamondbacks' Triple-A affiliate in Reno, Nevada, but had a clause in his contract that enabled him to opt out if he had a big league offer elsewhere.
He went 5-1 with a 4.50 ERA in six starts for Reno, with 35 strikeouts in 34 innings.
Information from The Associated Press was used in this report.