Introduction: Paying attention to puberty periods effects on different dimensions of adolescents' personality has an essential importance. Therefore, this study aimed to determine the effect of puberty health education on 12-14 year-old girls' mental health and identity styles.

Materials & methods : In this semi-experimental study using three groups with pre-test and post-test, 199 girls (10-14 year-old) were selected from schools in Ilam city using purposeful sampling and were educated in a ten-session course. Data were collected using Bersonsky Identity Style Questionnaire and Kumar Mental Health Check List.

Findings: The results of this study showed that puberty health education has an effect on mental health and normal identity style of 12-14 year-old girls', but has no effect on their physical health and other identity styles.

Discussion & conclusions: Normal identity style was created by following important people's life; furthermore, teachers and peers groups are important people in the life of each person in adolescence and puberty periods. Therefore, it can be said that this identity style was affected by puberty health education in comparison with other identity styles; this effect has been more in cooperative group that we used peers group education.