Introduction: It is now recognized that psychological disorders, among children and adolescents have high prevalence rate. Currently, there is limited data on the prevalence of mental health problems among adolescents especially in the developing country like Nepal. The objective of this study was to investigate the prevalence of mental health issues among school children aged 11-17 years. Materials and Methods: The self rated version of Strength and Difficulty Questionnaire (SDQ-YR1) were given to the students and answers were collected and the data was analyzed using SPSS version 16.1. The questions were in the Likert scale 0(not true), 1(somewhat true) and 2(certainly true). The data collected also included parent’s educational and occupational status. Results: A total of 159 students participated in the study after receiving well informed consent from the parents. There were 96(60%) boys and 63 (40%) girls’ participants in the study. Among all the participants in this study 18.6% had a total-Strength and Difficulty Questionnaire (SDQ) score that can be classified as abnormal by published cutoffs. The emotional problems (24.5%) and peer relationship problem (22%) were the two common problems screened as an abnormal SDQ score. Girls were significantly more likely to have emotional problems than boys (p value <0.05) where as boys were significantly more likely to have Hyperactivity/inattention score in SDQ than girls (p value<0.05).Gender difference was also significant statistically as girls had higher abnormal total SDQ score than boys (p value < 0.05). Conclusion: There is high prevalence of mental health issues in children but a study in large sample is recommended. DOI: http://dx.doi.org/10.3126/jnps.v33i3.8752 J. Nepal Paediatr. Soc. 2013;33(3):172-176