Background: In chronic illnesses, sexual dysfunction (SD) is one of the most prevalent complaints. Sexual self-efficacy (SSE) is an individual’s beliefs about his/her ability to perform an effective sexual function and be favorable to their partner. The aim of the present study was to assess SSE and sexual function in women with multiple sclerosis (MS). Methods: This cross-sectional study was carried out in 2019 on 260 married women referring to the MS clinic and MS society of Khorasan-Razavi in Mashhad, Iran. The research population was selected using convenience sampling. The Sexual Self-Efficacy Questionnaire (SSEQ), Multiple Sclerosis Intimacy and Sexuality Questionnaire-19 (MSISQ-19), and the Female Sexual Function Index (FSFI) were completed by the participants who had the inclusion criteria. The collected data were analyzed using descriptive statistics and Spearman's rank correlation coefficient in SPSS software. Results: The participants had a mean age of 35.2 ± 8.4 years and their mean duration of MS was 4.46 ± 3.71 years. The findings showed a negative correlation between SSE and SD (r = -0.606; P = 0.001) and a positive correlation between SSE and sexual function (r = 0.644; P = 0.001). Moreover, MSISQ-19 and FSFI scores supported each other (r = -0.675; P = 0.001). Conclusion: SD is prevalent among women with MS. Moreover, sexual function is substantially associated with SSE in these women.