Accommodation consists of changes in family members’ behavior to prevent or reduce patients’ obsessive–compulsive disorder (OCD) rituals or distress. High levels of family accommodation are associated with more severe symptoms and functional impairment in patients, and may also interfere with exposure-based treatment. The purpose of this study was to develop and test an intervention to reduce accommodation in the family members of adult OCD patients. Patients (N = 18, mean age = 35.44, 33% male, 94% Caucasian) received a course of standard individual exposure and ritual prevention (ERP) for OCD. Family members (N = 18, mean age = 41.72, 56% male, 94% Caucasian) were randomized to either receive or not receive the adjunctive intervention, consisting of two sessions of psychoeducation and skills training in reducing accommodation. Results revealed that the intervention successfully reduced scores on the clinician-rated Family Accommodation Scale (Week 8: d = 1.05). Patients whose family members received the intervention showed greater reductions in Yale-Brown Obsessive–Compulsive Scale scores across treatment than patients whose family members had not (Week 8: d = 1.27), and hierarchical regression analyses revealed that change in family accommodation from baseline accounted for a significant amount of variance in later OCD symptoms (β = .45, p = .02). Results from this preliminary study suggest that adjunctive intervention produces more rapid treatment response compared with traditional ERP alone. Accommodation is a potentially important target for improving treatment in OCD and other diagnostic groups where accommodation is likely to occur.