Abstract Background: Eating disorders (EDs) are a major public health issue faced by female students. The aim of this study was to evaluate the effectiveness of the educational program regarding eating disorders among Preparatory School Girls. Methods: The study employed a quasi-experimental research design. The study focused on four randomly selected secondary girls' schools in Assiut City, selected through a simple random sampling method. Multi stage random sample was used in this study. The sample size was 376 students. Data was collected using a self administered structured questionnaire which included demographic characteristics of students, Body Mass Index, assess the students' knowledge regarding eating disorders, The Eating Disorder Examination Questionnaire. Results: the study comprises younger adolescents aged 11-13 years (61.4%), with a significant majority residing in urban areas (97.1%), 16.3 % of them had eating disorders, 76.1% of participants following a non-vegetarian diet and 23.9% adhering to vegetarianism. the examined girls initially possessed inadequate knowledge (93.3%), following the program, three-quarters of them (75.0%) transited to a state of good knowledge. No significant differences were found between demographic characteristic in both pre and post-test knowledge scores. Conclusion: The findings indicate an improvement in knowledge scores and a positive effect on reducing concerns and behaviors associated with eating disorders. Recommendation: Further studies on larger sample size among different groups and settings are needed for generalization of the study.