Objectives: To assess the overall effect size of the impact of yoga on menstrual pain in primary dysmenorrhea. Methods: Randomized controlled trials that were published in the English language until December 2018 in PubMed, EMBASE, Web of Science, and the Cochrane Library electronic databases were searched. The methodologies from 4 trials conducted on 230 participants with primary dysmenorrhea were included in this meta-analysis to compare the effects that performing a yoga program has on menstrual pain (n = 129) to the effects of not performing yoga (n = 101). Results: The overall effect size of the impact of a yoga program on menstrual pain in primary dysmenorrhea was high with a standardized mean difference of -2.09 (-3.99 to -0.19) (p = 0.031) among the effect sizes of the 4 trials (95% confidence interval). Conclusions: Yoga is an effective intervention for alleviating menstrual pain in women with primary dysmenorrhea. Keywords: Menstrual pain; Meta-analysis; Yoga.