Background: Dysmenorrhea is one of the most common gynecologic disorders. It is the greatest single cause of lost work and school days among adolescent girls. The aim of this study was to assess knowledge, attitude and practice among adolescent girls regarding dysmenorrhea. Subjects and methods: A descriptive research design was utilized to fulfill the aim of this study. Purposive samples composed of 300 girl students were recruited from two governmental secondary schools. Tools for data collection were consisted of five tools:  a structure self-administrative interview questionnaire, visual analogue scale, knowledge assessment, attitude scale, and practice assessment. Results: 45.3% of the adolescent's girls had moderate pain, 41.3% of the adolescent's girls take analgesic during dysmenorrhea, 79.7% of adolescent's girls had unsatisfactory knowledge level, 87.0% of them had poor practice during dysmenorrhea, and 55.7% of them had positive attitude toward dysmenorrhea. Conclusion: about half of the adolescent's girls had moderate pain, more than one quarter of them had pain in lower abdomen, back, and legs and the majority of adolescent's girls had unsatisfactory knowledge level, poor practice during dysmenorrhea, but more than half of them had positive attitude toward dysmenorrhea.  Recommendation: initiate educational program during adolescent stage by using a multitude of audiovisual materials that suite for each adolescent's girls and achieve a satisfactory level