The Marlins recalled Kempner from Triple-A Jacksonville on Tuesday, Christina De Nicola of MLB.com reports.
He's grabbing the roster spot vacated by Chris Paddack, who was designated for assignment. Kempner holds a 6.46 ERA this season with Jacksonville but has struck out a whopping 34 batters over 15.1 innings. He will be making his major-league debut when/if he enters a game.