Objectives: The aim was to evaluate the validity and reliability of the persian version of Yale-Brown Obsessive- Compulsive Scale (Y-BOCS). Method: The sum of 140 patients with obsessive-compulsive disorder (OCD) and 30 individual participants without OCD were selected via convenient sampling as experimental and control groups respectively. Data gathering was done using Y-BOCS, Structured Clinical Interview for DSM-IV axis-I disorders (SCID-I) and Symptom Checklist-90-Revised Obsessive-Compulsive Symptoms (SCL-90-R-OCS). Reliability coefficients were calculated by Cronbach's alpha, split-half, and test-retest reliability. For validity assessment, concurrent criterion-related validity in correlation with SCID-I and SCL-90-R-OCS, and construct validity (exploratory factor analysis) were executed. In order to normalize the Y-BOCS after insuring that the distribution is normal and does not have kurtosis and skewness, mean and standard deviation were used as the most appropriate central tendencies and deviation. Results: Optimal levels of internal consistency scores (symptom checklist 0.97, severity scale 0.95) split-half reliability (symptom checklist 0.93, severity scale 0.89), and test-retest reliability (0.99) were calculated. Concurrent reliability were examined and established by correlating the Y-BOCS with the SCL-90-R-OCS and SCID-I. Exploratory factor analysis was also examined, which indicated three factors for symptom checklist scale and two factors for symptom severity scale. Cutoff point value (9) was also determined. Conclusion: The results supported satisfactory validity and reliability of translated form of Yale-brown Obsessive-Compulsive Scale for research and clinical diagnostic applications.