The purpose of this study was to assess the validity and reliability of the Oxford Happiness Questionnaire. For this aim 101 students of Allameh Tabatabai and Shahed Universities(39 male, 62 female) with a mean age of 22.5 (with an age range of 19 to 39) were studied. The study of the internal stability of the questionnaire showed that all the 29 items have high correlation with total scores, the Cronbach's alpha was 93% and split-half reliability was 92%. The assessed reliability by test-retest after 3 weeks was 79% (n=25). In order to evaluate the face validity of the questionnaire, ten experts approved the power of evaluation of happiness by this test. The factor analysis, revealed 5 factors which could explain 57.1 % of the total variance. This finding differs from the findings reported by the author of the questionnaire. Based on the findings of this research, it seems that this questionnaire is quite appropriate for measuring the degree of happiness of university students in Tehran.