Introduction: Today, computer games have become an integral part of the lives of children, adolescents, young adults and adults. This study aimed to explore the impact of computer games on mental health of secondary school students (third grade) in schools of 19 stricts of Tehran, Iran.

Methods: The method of study was retrospective, and pretest-posttest type. The study sample consisted of students in third-grade primary schools in Tehran. The sample size was selected using Cochran formula (897). The research tools were mental health and research-made questionnaires. The validity of the latter was verified by A.P experts and relevant specialists. The reliability of the research was validated based on Cronbach’s coefficient as 0.79. Data analysis was conducted using descriptive statistics (tables of tendency to center and distribution indexes and frequency tables) and inferential statistics (one-way ANOVA) as well as SPSS software.

Results: The significance level obtained for the relationship between the use of computer games and different aspects of health were as follows: aggression 0.001, depression 0.002, anxiety 0.003, interpersonal sensitivity 0.003, less than (0.005). The results reject the null hypothesis for all the research hypotheses, and hypotheses regarding the relationship between the use of computer games and various aspects of health were confirmed.

Conclusions: The research findings statistically suggest that students who do not play computer games are in much better conditions in terms of mental health level in all dimensions (aggression, depression, interpersonal sensitivity and physical symptoms) compared with students who play more or less. Furthermore, planning to optimize the use of leisure time in students can prevent the spread of inappropriate games.