Symptom reduction over the course of cognitive-behavioral therapy is not always distributed evenly across sessions. Some individuals experience a sudden gain, defined as a decrease in symptom severity between two consecutive sessions that is large (a) in absolute terms, (b) compared to severity before the gain, and (c) compared to fluctuations before and after the gain. Although research documents a link between sudden gains and treatment for depression and anxiety, findings in the context of obsessive-compulsive disorder (OCD) treatment are mixed. The present study investigated the relationship between sudden gains and treatment outcome in 44 adults with OCD and addressed limitations of previous studies by measuring OCD symptoms dimensionally and comparing individuals who experience sudden gains to those who experience gradual gains of similar magnitude. Sudden gains were observed among 27% of participants, with highest rates among individuals with primary contamination symptoms. Participants who experienced a sudden gain had greater OCD symptom reductions at post-treatment (but not at follow-up), and this difference did not persist after controlling for gain magnitude. Thus, the importance of sudden gains during OCD treatment may be limited. Findings are discussed in light of inhibitory learning models of cognitive-behavioral therapy.