The chemical treatments of primary dysmenorrhea have some side effects. Therefore, the present study was conducted to compare the efficacy of Extra Virgin olive oil and Ibuprofen for treatment of primary dysmenorrhea among female students. Materials and Methods: In a single blinded crossover clinical trial, female single students 17-30 years old, moderate and sever primary dysmenorrhea were enrolled to the study. Chronic disease, allergies, pelvic or abdominal surgery, stressors in the past two months, irregular menstrual cycles, use of oral contraceptives during 3 months ago were excluded from the study. Screening for primary dysmenorrhea was done by a visual analog scale.Participants were randomly divided into two groups. The participants were followed up for 5 menstruation cycles. The subjects in group 1 took 25 cc of extra virgin olive oil daily for 2 months (starting two weeks before the start of the menstruation cycle) and completed a questionnaire containing items on pain visual analogue scale for two consecutive cycles. After a 4-week washout period they received 400 mg Ibuprofen three times a day in the first 3 days of menstruation. Group 2 was treated basically similarly, except that they received Ibuprofen during the two first cycle and extra virgin olive oil during the two second cycle. The collected data were analyzed using the descriptive and inferential statistics, t-test and linear mixed models. The pain severity difference was significant before and after intervention in both groups. The pain severity decreased to 3.8 ± 2.2 after intervention in Ibuprofen group and 1.1 ± 0.8 after intervention in Extra Virgin olive oil group. There was a significant difference in pain severity between the two groups after the intervention (P= 0.001). The Extra Virgin olive oil is effective in primary dysmenorrhea. It is recommended as a food supplement.