Family accommodation in obsessive compulsive disorder (OCD) consists of participation in symptoms and modification of family routines in order to reduce patients' anxiety and impairment, manage relatives' own distress, and maintain family functioning. Higher levels of accommodation are associated with increased symptom severity and worse treatment outcome. However, this has not been investigated for adults with OCD receiving intensive cognitive behavioral therapy (iCBT). The aim of this study was to examine if change in family accommodation during the intensive phase of iCBT predicted treatment outcome. Within an observational study design, 52 adult patients received iCBT with pre-, between- and post-treatment measurements. Results showed that family accommodation was reported by 94% of relatives of OCD patients and was associated with self-reported OCD symptoms but not global functioning. Family accommodation was significantly reduced from pre-to post-treatment. Greater reductions in family accommodation were associated with lower levels of OCD symptom severity and better global functioning at post-treatment, and greater likelihood of achieving remission status. However, changes on the outcome measures from pre-to post-treatment were not dependent on the magnitude of change in family accommodation during the intensive phase of treatment. Therefore, findings are inconclusive in supporting that targeting family accommodation might directly affect treatment outcome for adults with OCD receiving iCBT