Introduction: Lack of sexual satisfaction and lack of sexual self-efficacy are common problems in women, affecting the quality of marital life. The present study was conducted with the aim of evaluating the effect of vitamin D on sexual satisfaction and self-efficacy in women of reproductive age. Methods: This clinical trial study was conducted on 102 women with sexual dysfunction and vitamin D level less than 30 ng / ml referring to health centers affiliated to Jundishapur University of Medical Sciences in Ahwaz in 2018. The research tools included Demographic Characteristics Questionnaire, Beck Depression Questionnaire, Larsson Sexual Satisfaction Questionnaire, and Sexual Self-efficacy Questionnaire. The research participants were randomly assigned into two groups of experimental and control (each group contained 51 people). The experimental group received oral vitamin D supplement in a dose of 1000 units per day and the control group received placebo (for 12 weeks). After the completion of the study, all the research samples completed the sexual satisfaction and sexual self-efficacy questionnaires and the levels of vitamin D were measured. Data were analyzed using Chi-Square test, independent t-test and SPSS 22 software. P value less than 0.05 was considered significant. Results: The mean score of sexual satisfaction and sexual self-efficacy was higher in the experimental group than that in the control group after the intervention, and this difference was statistically significant (p <0.001). Conclusion: Vitamin D supplement increases sexual satisfaction and self-efficacy in women of reproductive age.