Background: Acne vulgaris is one of the commonest skin disorders which dermatologists have to treat, mainly affect adolescents, though it may present at any age. Acne is definited as multifactorial chronic inflammatory disease of pilosebaceous . The study aimed to Assessment of adolescents students' knowledge and attitude toward acne vulgaris in secondary schools .Subjects and methods descriptive research cross sectional design was used. The study was conducted in four secondary schools .The total study sample was 1026 students which were selected randomly. Tools of the study: the study included two tools: first tool was self administered structure questionnaire, which included two parts; first part included demographic characteristics of studied students, second part included knowledge about acne. The second tool was likert scale to measure attitudes toward acne. Results: It was found that 67% of studied students were female. The majority (91.1%) of studied students had poor knowledge about acne. Also, it was found that 61.9% of studied students had positive attitude Conclusion: The majority of the studied students had poor knowledge about acne and more than three fifth of them had positive attitude toward acne. Recommendations: School health nurses should be attended the educational programs about acne because they are most contact and deal with the students.