Background: Primary dysmenorrhea is a common gynecological condition that negatively affects daily functioning and quality of life in young women. Non-pharmacological interventions such as progressive muscle relaxation exercises (PMRE) may provide supportive benefits in symptom management. Aim: This study aimed to evaluate the effects of PMRE on pain intensity, menstrual symptoms, and quality of life in young women with primary dysmenorrhea. Methods: This single-center, parallel-group randomized controlled trial included 42 young women with primary dysmenorrhea who were randomly assigned to intervention and control groups. Pain intensity, menstrual symptom intensity, and quality of life were assessed across two menstrual cycles. The trial was registered at ClinicalTrials.gov (NCT05340101). Results: Menstrual symptom intensity and pain scores were significantly lower in the intervention group compared with the control group (p <.001). A significant between-group difference was observed in the mental component of quality of life in favor of the intervention group (p =.001), whereas no significant difference was found in the physical component (p >.05). Repeated-measures analyses also demonstrated significant time effects and group × time interactions, indicating a reduction in dysmenorrhea intensity over time in the intervention group (p <.05). Conclusion: PMRE was associated with reductions in dysmenorrhea intensity and menstrual symptoms, as well as improvements in the mental component of quality of life. These findings suggest that structured relaxation exercises may serve as a feasible complementary approach for symptom management in primary dysmenorrhea.