Background and aim: Melissa officinalis was traditionally used for pain relief and treatment of some diseases. The aim of the study was to compare the effect of mefenamic acid and Melissa officinalis (Melissa) on pain management in primary dysmenorrhea. Methods: In this clinical trial, forty-three eligible women with moderate to severe primary dysmenorrhea were randomly allocated into the Melissa officinalis and mefenamic acid groups. The mefenamic group received 250 mg capsules every 8 hours from the onset of menstruation pain until pain relief for three consecutive cycles, and the Melissa group used one tea bag in the same manner. The intensity and duration of menstrual pain were assessed by the visual analog scale and a self-reported questionnaire. Data were analyzed using student t-test, Chi-square and ANOVA. Results: The intensity and duration of pain in both groups showed a significant descending trend (In both groups P<0.001); however, this trend was greater in Melissa group in terms of pain intensity (P=0.008), with no significant difference on pain duration (P=0.101). Conclusions: Melissa was more effective than mefenamic acid in relief of pain on primary dysmenorrhea. Regarding to safety of Melissa, it could be considered as an alternative treatment for primary dysmenorrhe
