Cast of Brittany Runs a Marathon

Jillian Bell portrays the lead character Brittany Forgler, a young woman who transforms her life by taking up running.

Michaela Watkins plays Catherine, Brittany's supportive neighbor and friend who inspires her to start running.

Utkarsh Ambudkar portrays Jern Dahn, a fun-loving and charismatic running enthusiast who becomes Brittany's running partner.

Lil Rel Howery plays Demetrius, Brittany's brother-in-law, who provides her with encouragement and motivation throughout her running journey.

Micah Stock portrays Seth, Brittany's roommate and friend who joins her in training for a marathon.

Alice Lee plays Gretchen, one of Brittany's close friends, who supports her in her pursuit of a healthier lifestyle.

Patch Darragh portrays Doctor Falloway, a medical professional who helps Brittany on her path to wellness.

Peter Vack plays Ryan, a potential love interest who enters Brittany's life and encourages her to embrace her newfound confidence.