Background: Preparatory School Students are a vulnerable group; they may be prone to high pattern of electronic devices usage which leads to negative effects on their health. So, the prevention of health hazards related to Usage of electronic devices is particularly important. Aim: The study aimed to evaluate effect of Prevention program of health hazards related to usage of electronic devices among preparatory school students. Study design: A quasi-experimental design was used to conduct this study. Subject: Multistage sample composed of eight hundred preparatory school students. Setting: This study was conducted at 19 governmental preparatory schools at El Sharabeya, and El-Zawia El- Hamra administrations for male and female students. Tools: It is composed of two-tools. The first tool is a self-administered questionnaire to assess socio- demographic characteristics, pattern of internet use, social and psychological health condition of students. The second tool is a physical assessment to assess their physical health status. Results: The result of this study showed that 33.5% of preparatory school students were aged 13 years old, 69% was males. 10.5% of students spent more than eight hours online and 79% of them use internet through mobiles or tablets, 28% of students' body weight increased, 46.5% of their sleeping pattern affected because of electronic devices, and 53% of them suffered from neck and backache after browsing the internet. Conclusion: The study concluded that there was statistically significant efficacy of the prevention program on improving the health pattern for school children and their knowledge about prevention of health hazards related to usage of electronic devices. As well, the program had significant effect on decreasing the negative effect of physical, social, and psychological health hazards, in addition to enhancing scholastic achievement through program implementation phases with significant statistical difference (P<.0001). (P<.0001). Recommendation: The study recommended that periodical health education about prevention of health hazards related to usage of electronic devices is necessary to raise school children's awareness and improve their health status and scholastic achievement.