BACKGROUND AND OBJECTIVES: Dysmenorrhea is a set of painful manifestations appearing the day before or during the first menstrual cycle day. Pilates is a series of exercises based on progressive movements the body is able to perform. This study aimed at comparing pain in women with primary dysmenorrhea before and after being submitted to Pilates. METHOD: This is a descriptive, experimental study with longitudinal characteristic and quantitative approach. A clinical evaluation was performed in10 Physical Therapy students, Center of Unified Teaching, Teresina (CEUT), aged between 18 and 30 years, with primary dysmenorrhea, who were submitted to a protocol of 16 Pilates floor and ball exercises aimed at the pelvic region. Pain intensity was evaluated by the visual analog scale and pain characteristics were evaluated by the McGill questionnaire. RESULTS: Mean pain value during menstrual cycle before treatment was 7.89 ± 1.96, and after treatment it was 2.56 ± 0.56 (p < 0.001). McGill questionnaire has shown significant improvement of all pain components after treatment: sensory (p < 0.001), affective (p < 0.005), evaluative (p < 0.001) and miscellaneous (p < 0.001). CONCLUSION: Pilates, as physical activity practice, has provided improvement of symptoms associated to primary dysmenorrhea, positively interfering with decreasing pain and representing a promising non-pharmacological alternative.