The aim of this study was translation and validation of the Duke University Religion Index in Iranian Muslims. The study was performed in two stages. In the first stage, 1,762 college students from Qazvin city with an average age of 21.2 years participated in the study. In the second phase, 796 college students with an average age of 23.7 were recruited from Tehran. A demographic questionnaire, Santa Clara Strength Faith questionnaire (SCSORF), and Duke Religion Index (DUREL) were administered. Cultural adaptation of these measures was performed by a forward-backward translation technique. Test-retest reliability and intraclass correlation coefficients (ICC) were used for assessing reliability. Convergent validity was measured by Spearman correlation between DUREL and SCSORF. Explanatory and confirmatory factor analyses (EFA and CFA) evaluated the factor structure. Results showed that the scale is reliable. Cronbach's alpha ranged from 0.866 to 0.921 and ICC ranged from 0.937 to 0.991. Correlations between DUREL and SCSORF were also strong (ranging from 0.62 to 0.79). Results obtained from CFA and EFA confirmed one-dimension for the DUREL. Thus, the DUREL appears to be a proper measure for assessing religiosity among Iranian Muslims. Further testing of the scale among minorities and those with special health-related conditions is suggested.