In addition to his acting career, Rash is also a successful filmmaker. His directorial debut, The Way, Way Back, received critical acclaim and was a box office success. Rash has also directed episodes of such television series as Community, Parks and Recreation, and Fresh Off the Boat.
In 2011, Rash was diagnosed with stage 2 non-Hodgkin's lymphoma. He underwent treatment and went into remission the following year. Rash is an advocate for cancer awareness and has spoken publicly about his experience with the disease.
Rash is married to writer Amy Pascal. They have two children together.