Vulvitis is considered one of the most common inflammatory conditions that occurs in the lower female genital tract and constitutes a considerable problem for many females causing ascending infection as well as anxiety and discomfort which was affecting the female's quality of life. The aim of the study was to evaluate the effectiveness of an instructional module on vulvitis prevention among adolescent girls. Method: A quasi-experimental design was utilized. Sample: A purposive sample of 200 adolescent girls was included in the current study. Setting: The study was carried out at industrial secondary school and joint commercial secondary school at menouf city. Instruments: A structured self- administrated questionnaire, knowledge assessment questionnaire, Modified Likert Scale and adolescent girls' satisfaction scale. The results revealed that 1) There was a highly statistically significant difference between both groups regarding all knowledge and attitudes items one-month post intervention (P <0.0001) compared to pre intervention. 2) All adolescent girls in the study group were satisfied about the instructional module concerning vulvitis and its preventive measures. Conclusion: Instructional module was effective and had positive effects on enhancing of adolescent girls' knowledge and attitudes regarding vulvitis and its preventive measures in the study group compared to the control group. Recommendation: Instructional module should be included as components adolescence education curriculum as active steps to increase awareness of adolescent girls regarding vulvitis and its preventive measures through schools, community and cultural groups.