Considering the importance of mental health in adolescents, we studied the prevalence of obsessive-compulsive disorder (OCD) in this age group and determined its relationship with their religious attitudes. In this survey, 293 students at different grades were selected using a multiphasic cluster sampling method. Subjects were asked to complete demographic, Yale-Brown scale, and religious attitude questionnaires. Those with scores higher than the cutoff value were interviewed by a psychiatrist, based on the DSM-IV criteria. Data were analyzed by chi2 and Student's t-test. The prevalence of OCD was 8.87% (5.1% in boys and 3.75% in girls). The majority of patients with OCD were from urban regions and had a positive family history in their first- or second-degree relatives. Nonetheless, there was no relationship between OCD and religious attitudes. The prevalence of OCD found in our study was higher than many of those reported earlier. Religious attitudes could only affect the contents of obsession and compulsion.