Vitamin D receptor (VDR) expression in the female reproductive tract explains the regulatory role of vitamin D on inflammatory cytokine and prostaglandin (PGD) synthesis. This study aimed to evaluate the effect of vitamin D on adolescents' primary dysmenorrhea and the relationship between Vit. D and adolescents' primary dysmenorrhea. Eighty-five adolescents were included in the current study. After a detailed evaluation, pelvic sonography was performed for all participants to rule out any pelvic pathology. Blood samples were collected to measure thyroid stimulating hormone (TSH), prolactin, glycosylated hemoglobin (HbA1C), and 25-hydroxyvitamin D (25[OH]D). Participants were administered vitamin D (50,000 IU weekly for five months), and their dysmenorrhea symptoms were evaluated before and after this period using the Visual Analog Scale (VAS) and the Verbal Multidimensional Scoring (VMS). The mean VAS and VMS scores of dysmenorrhea statistically decreased from 8.7±0.91 and 2.65±0.93 to 4.8±0.75 and 0.80±0.75, respectively, after vitamin D intake (p=0.03 and 0.025, respectively). Significant negative associations between 25(OH)D and VAS (R = -0.886; p<0.00001) and VMS of dysmenorrhea (R = -0.885; p<0.00001) were detected in this study. Vit. D could be a useful therapeutic option to reduce the severity of primary dysmenorrhea and could limit the use of non-steroidal anti-inflammatory drugs.