Objectives The prevalence of non-communicable diseases is increasing in Nepal. Overweight and obesity are the major risk factors of many non-communicable diseases. Adolescence is a critical phase for development of overweight and obesity. Risk factors associated with overweight and obesity are not well understood in Nepal. The objective of the study was to identify the factors associated with overweight and obesity among adolescent students.

Setting A cross-sectional descriptive study was carried out on higher secondary school students in the Lalitpur sub-metropolitan city, Nepal.

Participants A random sample of 360 students aged 16–19 years from eight schools was included in the study.

Results The prevalence of overweight among adolescent students was 12.2% (95% CI 8.9 to 15.5). Factors associated with being overweight included being male (adjusted OR (AOR) 2.64, 95% CI 1.18 to 4.88), studying in private school (AOR 2.10, 95% CI 1.03 to 4.28), high socioeconomic status family (AOR 4.77, 95% CI 1.36 to 16.72), watching television for more than 2 h per day (AOR 8.86, 95% CI 3.90 to 20.11), and consuming fruit four times or less per week (AOR 3.13, 95% CI 1.39 to 7.01). There was no statistically significant association between adolescent overweight and age, ethnicity, mother's education level, mother's occupation, number of siblings or family type.

Conclusions Socioeconomic status, watching television for a longer time and consuming less fruit are major risk factors for overweight among adolescents in Nepal. Interventions are needed to increase awareness about the risk factors of adolescent overweight and obesity to decrease prevalence of overweight-associated non-communicable diseases.