Abstract Family accommodation is the term used to indicate the process whereby family members of patients with obsessive–compulsive disorder (OCD) assist or participate in the patients' rituals. Family accommodation is a relatively under-researched phenomenon in OCD but an important one because it may be predictive of poor treatment outcome. This study systematically examined several socio-demographic and clinical variables that are associated with family accommodation in a well-characterized sample of adult patients and their healthy family members. Experienced clinicians administered the Family Accommodation Scale (FAS) to 141 psychopathology-free family members cohabiting with 97 patients with OCD. The items of the FAS were first subjected to principal component analysis (PCA) and the resulting domains of family accommodation (Participation, Modification, and Distress and Consequences) introduced as dependent variables in a series of multiple regression models assessing the relationship between family accommodation domains and a wide range of clinical variables, including Axis I and II psychopathology and symptom dimensions derived from the Yale–Brown Obsessive–Compulsive Scale (YBOCS) Symptom Checklist. The results showed that family accommodation was common, with the provision of reassurance, participation in rituals and assisting the patient in avoidance being the most frequent practices (occurring on a daily basis in 47%, 35%, and 43% of family members, respectively). The PCA of the YBOCS Symptom Checklist yielded four symptom dimensions, which were identical to those previously identified in the international literature. Multiple linear regression analyses showed that a higher score on the contamination/washing symptom dimension and a positive family history for an anxiety disorder other than OCD (referring to a family member other than the participant in this study) predicted greater scores on several domains of family accommodation. Our study confirms that family accommodation is frequent and distressing in psychopathology-free family members cohabiting with adult OCD patients. Family accommodation is particularly frequent and distressing when the patient has prominent contamination/washing symptoms and/or when another family member has a history of an anxiety disorder. Such families may be more likely to benefit from family-based interventions but this remains to be tested in controlled trials.