Abstract Objective To investigate the effectiveness of montelukast, a leukotriene receptor antagonist, in alleviating the symptoms of dysmenorrhea. Study design This prospective, double-blind, randomized, placebo-controlled study was comprised of 62 patients with dysmenorrhea who were randomly divided into 2 groups (montelukast and placebo). Data obtained from 50 patients were analyzed (montelukast: 24; placebo: 26). Using visual analog scale (VAS) scores and nonsteroidal anti-inflammatory drug (NSAID) usage per menstrual cycle, values before treatment were compared to average scores over two menstrual cycles with treatment. Results Both the VAS scores and NSAID usage decreased significantly in both groups. The decreases were greater in the montelukast group compared to the placebo group, but the differences were not statistically significant. Nevertheless, in “highly effective cases,” which were defined as having a post-treatment value less than half of the pre-treatment value, the decreases were significantly greater in the montelukast group than in the placebo group (VAS: montelukast, 4 vs. placebo, 0 ( P = 0.029); NSAID: montelukast, 9 vs. placebo, 3 ( P = 0.031)). Conclusions The present study found that montelukast may be effective in alleviating pain associated with dysmenorrhea in some women. Montelukast is safe and does not influence hormonal levels. Therefore, montelukast is a clinically reasonable management option to consider before prescribing a hormonal agent.