The new Fox series follows Mindy Kaling's character, a single women working at a hospital as a doctor.
Both Setton and Tobolowsky will be featured full-time on The Mindy Project, while Barinholtz will have a recurring role, reports Entertainment Weekly.
Setton, who is known for her role in Gossip Girl, will play Shauna Dicanio, the hospital's tough, Jersey-born office manager.
She is also described as "a woman who collects unpaid patient bills like she's a bounty hunter".
Meanwhile, Glee actor Tobolowsky will star as Dr. Marc Shulman, the head of the practice who is said to enjoy giving advice, especially if it "gets his younger staff to leave him alone".
Barinholtz, who is also the show's executive story editor, will portray an ex-con-turned-male nurse named Morgan Tookers, who is loyal to his co-workers.
The Mindy Project makes its series debut on Tuesday, September at 9.30pm ET on Fox.
Watch a new trailer for The Mindy Project below: