Perfectionism is known to be highly prevalent in obsessive-compulsive disorder (OCD). This review seeks to explore perfectionism in OCD and related disorders, particularly in relation to treatment, in order to inform treating clinicians. We also evaluate the potential role of perfectionism in the maintenance of OCD. Evidence supports perfectionism as a transdiagnostic process central to the psychopathology of OCD and other mental illnesses. Treatment outcomes in EX/RP for OCD are diminished in the presence of perfectionism, which is thought to be due to inherent treatment interfering features of perfectionism. Successful OCD treatment has been shown to decrease perfectionistic thinking, though data are mixed on whether reducing perfectionism mediates subsequent reductions in OCD symptoms. Short-term cognitive behavioral protocols for perfectionism are reviewed here and recommendations are made for the treatment of perfectionism in the context of OCD and related disorders.