Background: Scrupulosity is a common yet understudied presentation of obsessive compulsive disorder (OCD) that is characterized by obsessions and compulsions focused on religion. Despite the clinical relevance of scrupulosity to some presentations of OCD, little is known about the association between scrupulosity and symptom severity across religious groups. Aims: The present study examined the relationship between (a) religious affiliation and OCD symptoms, (b) religious affiliation and scrupulosity, and (c) scrupulosity and OCD symptoms across religious affiliations. Method: One-way ANOVAs, Pearson correlations and regression-based moderation analyses were conducted to evaluate these relationships in 180 treatment-seeking adults with OCD who completed measures of scrupulosity and OCD symptom severity. Results: Scrupulosity, but not OCD symptoms in general, differed across religious affiliations. Individuals who identified as Catholic reported the highest level of scrupulosity relative to individuals who identified as Protestant, Jewish or having no religion. Scrupulosity was associated with OCD symptom severity globally and across symptom dimensions, and the magnitude of these relationships differed by religious affiliation. Conclusions: Findings are discussed in terms of the dimensionality of scrupulosity, need for further assessment instruments, implications for assessment and intervention, and the consideration of religious identity in treatment.