Obsessive-compulsive disorder (OCD) is an impairing psychiatric condition that is characterized by obsessions (i.e., intrusive thoughts, images, or urges) and compulsions (i.e., repetitive actions aimed at preventing or reducing distress). Much research has focused on serotonin as a critical neurotransmitter in OCD, yet there is a growing work suggesting alterations in dopamine systems in OCD. Dopamine is a key neurotransmitter with a widespread impact on many adaptive neurocognitive functions and alterations in mental health. Animal research has linked dopamine to repetitive and compulsive-like behaviors. Human brain imaging suggests increased striatal dopamine neurotransmission in adult OCD. Genetic studies provide mixed results with potentially sex-specific effects. Treatment research highlights a role for dopaminergic medications to augment standard serotonin treatments, particularly for treatment-resistant patients. New work leveraged a novel, non-invasive neuromelanin-sensitive imaging approach to identify increases in midbrain dopamine functioning in pediatric OCD. Taken together, this body of research supports a role for dopamine brain circuits in the etiology and treatment of OCD.