Background: Adolescent overweight/obesity is increasing worldwide at alarming rate in both developed and developing countries. The prevalence of overweight among adolescents was become an emerging problem in Ethiopia. In Bahir Dar city the overall prevalence of overweight and obesity was 16.7%. Although some studies were conducted on prevalence and associated factors of overweight in Ethiopia, still there is limited data on determinants of overweight among high school adolescents in Ethiopia including the study area. Objective: To identify determinants of overweight/obesity among high school adolescents in Bahir Dar City, Ethiopia. Methods: School based unmatched case-control study design was employed from March 01-13/2020. Sample size of 297 was calculated by using Epi info and multistage systematic sampling technique was used for sample selection. Data was collected through pre tested self-administered questionnaires by trained data collectors. Data was coded and entered into Epi Data version3.1. Then it was exported to SPSS version 23 for analysis. Bivariable and multivariable logistic regression analysis were employed for Crude and Adjusted odds Ratio. The goodness of fit of the final logistic regression model was checked using the Hosmer- Lemeshow technique that p-value >0.05 indicates a good model. Result: Mother education level (AOR=5.58, 95%CI:1.35-23.12), Screen viewing (AOR=5.64, 95%CI:2.5-12.7), Sleep duration (AOR=6.59, 95%CI:1.8-23.7), vehicle transport (AOR=5.2 95%CI:2.18-12.5), meal frequency (AOR=5.63, 95%CI:2.37-13.38) were positively associated with the likelihood of having overweight, whereas vegetable intake (more than once per day (AOR=0.061, 95%CI:0.01-0.3), once per day (AOR=0.084, 95%CI:0.01-0.66), 5-6 times per week (AOR=0.117, 95%CI:0.024-0.56) and1-4 times per week (AOR=0.127, 95%CI:0.022-0.73)) and parental monitoring (AOR=5.59, 95%CI:2.4-12.89) were negatively associated with the likelihood of having overweight. Conclusion and recommendation: The study showed that, mother education level, screen viewing, sleep duration, Vehicle transport, meal frequency, vegetables and parental monitoring were important determinants of overweight in adolescents. preventive intervention Strategies that address these determinant factors of overweight should be designed by concerned bodies and implemented at every setting to prevent overweight/obesity and related chronic diseases. Key Words: Adolescents, overweight/obesity, determinant factors, Bahir Dar City