Introduction: Happiness is one of the most effective factors in economic, cultural, social, and political development in a society that reduces family problems, divorce, increased academic achievement, job engagement, and production. This study aimed to determine the relationship between self-efficacy and happiness variables with some demographic variables among a group of students. Method: This cross-sectional study was performed on 371 students from Mazandaran University of Medical Sciences who met the inclusion criteria and selected by simple random sampling method in 2018-2019. The data were collected using Oxford Happiness Inventory (OHI) and General Self-efficacy Scale (GSE). Data analysis was performed by SPSS23 using student t-test, one way ANOVA, and Pearson correlation tests. Result: The mean age of the subjects was 22. 23 ±, 2. 95 years, the mean score of happiness was 28. 65 ±, 14. 81, and the mean score of self-efficacy was 60. 5 ±,9. 44. The variables of age, sex, and education were significantly associated with happiness (P <0. 05). Self-efficacy was also significantly associated with age, sex, marital status, and educational level (P <0. 05). Conclusion: Some demographic variables are effective in happiness and self-efficacy in students. In order to promote mental health and the importance of happiness in students, it is recommended to assess these variables, and then take appropriate planning strategy.