Background: According to the importance of postpartum sexual dysfunctions and their effects of these cases on the quality of life of the couple, this study aimed to determine vaginal postpartum sexual function and dyspareunia. Methods: This descriptive-analytical study was performed on 400 women with a history of natural childbirth in 2020 - 2021 in Hormozgan Province, Iran. The demographic and obstetric checklist, sexual function, and postpartum dyspareunia questionnaires (Carol Scale) were used. For data analysis, “SPSS 18.0” Software and for Partial least squares (PLS) modeling, Smart PLS Software was used. Results: The mean age of the women was 26.74 ± 6.12 years, and the average overall sexual function and postpartum dyspareunia score were 27.18 ± 8.62. All amounts of cross-validated communality indicated the appropriate and acceptable quality of the present research model. The absolute goodness of fit (GOF) for the tested model was 0.41, indicating the tested model's appropriate fit. Age, spouse age, education, the average number of intercourse, and marital satisfaction directly affected sexual function after vaginal birth. In contrast, age, spouse age, education, duration of marriage were indirectly correlated with sexual function after vaginal birth through marital satisfaction (P < 0.01). In the present study, age, spouse, and education had a direct and indirect effect on sexual function after vaginal birth. Conclusions: Poor marital satisfaction can cause sexual dysfunction after vaginal delivery. Therefore, it is hoped that by using the present study results and similar ones to identify the factors affecting sexual function, by training couples and healthcare providers, sexual relations and emotional performance between couples will be established and strengthened more than before.