The Lifetime series follows Deb, a vapid aspiring model who is killed in a car crash on her way to an audition and brought back to life as the plus-sized lawyer Jane.
Feldman plays Deb/Jane's guardian angel named Fred.
He will reprise his role in the season four finale on September 9, reports Entertainment Weekly.
Last month, Feldman received an Emmy nomination for his Mad Men character Michael Ginsberg, who often clashed with Jon Hamm's Don Draper.
Speaking about his Mad Men role, Feldman joked that he thought Hamm hated him.
Feldman said: "When [Jon is] in character, he's in character, and there were moments where I was wondering, 'Wait, does Jon kind of hate me?'"
Watch a season four promo for Drop Dead Diva below: