Our objective was to examine the effect of an Iranian herbal drug in the treatment of primary dysmenorrhea. A randomized, double-blind, placebo-controlled pilot trial among 180 female students at Isfahan University dormitory aged 18 to 27 who suffered from primary dysmenorrhea was undertaken. The participants were randomly divided into three groups: herbal drug, mefenamic acid, and placebo. The herbal drug group was given 500 mg of highly purified saffron, celery seed, and anise (SCA) extracts three times a day for three days, starting from the onset of bleeding or pain. Participants were followed for two to three cycles from the beginning of menstruation through the three days of bleeding. Main outcome measures were the severity and duration of pain at 2 and 3 months. A visual analogue scale was used to record pain. There were statistically significant reductions in pain scores and pain duration scores in the groups that took SCA (P < .001) and mefenamic acid (P < .01). The decrease in pain score was reflected by a significant reduction in other drug use among the treatment groups compared with the women in the placebo group. The magnitude of the reduction was significantly greater in the SCA group than in the mefenamic acid and placebo groups. Both drugs effectively relieved menstrual pain as compared with the placebo. More clinical trials are needed to establish the efficacy of this herbal drug.