Study aim: Determining the effect of self-regulation training based on the Leventhal model on the severity of Premenstrual Syndrome (PMS) Symptoms Design: A randomized controlled clinical trial will be conducted on 78 nursing students, who will be randomly allocated to intervention and control groups using computer-generated randomization with a 1:1 allocation ratio Settings and conduct: This study is conducted at the School of Nursing and Midwifery, Tehran Islamic Azad University of Medical Sciences. Seventy-eight students are randomly allocated to intervention and control groups using computer-generated randomization (1:1). The intervention group receives Leventhal’s self-regulation training, while the control group receives no education. Data are collected at baseline, immediately post-intervention, and 8 weeks later. Participants/Inclusion and exclusion criteria: Inclusion criteria: Regular menstrual cycles during the past 6 months; being single; presence of moderate to severe PMS ; normal Body Mass Index Exclusion criteria: History of gynecological diseases; diagnosed psychiatric disorders; use of psychiatric medications; alcohol or tobacco use; presence of vaginal infection; and exposure to major stressful life events (e.g., death of a close relative) within the past three months. Intervention groups: The intervention group will receive Leventhal’s self-regulation training in four weekly 60-minute sessions, while the control group will not receive any training. The content of the sessions includes introducing illness perceptions, identifying and modifying maladaptive beliefs, teaching emotion regulation, practicing coping skills, and designing an individualized symptom -management plan. Main outcome variables: Severity of premenstrual syndrome