Background: Overweight and obesity can be defined as “abnormal or excessive accumulation of fat that may impair health” and formally recognized as a global epidemic in 1997 by WHO. The prevalence of overweight and obesity in adolescent is increasing worldwide, and currently over 340 Million adolescents were overweight or obese. Overweight/obesity is risk factors for many chronic diseases and is becoming a double burden of malnutrition to Ethiopian. There was no information regarding prevalence and contributing factors of overweight and obesity among high school students Bahir Dar City (study area). Objective: To assess the prevalence of overweight/obesity and associated factors among high school students in Bahir Dar City, North West Ethiopia, 2021. Method: - Cross-sectional study design was conducted from October 1/2020 to November 30/2020 among high school adolescents’ in Bahir Dar, Ethiopia. Data was entered into Epi data 3.1 and exported to SPSS version 26 software for analysis and BMI for age computed using WHO Antropus. Result: The overall prevalence of overweight and/or obesity was found to be 18.7 % which overweight and obesity 13.7% & 5% respectively. The prevalence of overweight & obesity among government school were 6.74 % & 1.98% respectively. The prevalence of overweight/obesity among private schools was 6.94 % & 2.9% respectively. Having higher and medium family socioeconomic status (AOR=3.05 95% CI; 1.59-5.82), and AOR=3.58(95%CI;1.74-7.35) respectively, adolescents age of 15-16 years AOR=1.99(1.17-3.39), milk, cheese and yoghurt consumption AOR=2.75(1.28-5.91), <3meal/day AOR=2.38(1.27-4.43), skipping dinner consumption/day AOR=2.04(1.15-3.64) and sedentary behaviour (sitting) ≥8 hours AOR= 2.487 95%CI;1.31-41) were significantly associated with overweight/obesity. Conclusions and Recommendation: the findings of this study show that there is increasing prevalence rates of overweight and obesity among high school adolescents of Bahir Dar city. Factors such as family higher and middle socioeconomic status, age, milk and dairy product consumption, meal per day, dinner consumption and sedentary behaviour sitting time spent were important determinants of overweight/obesity in adolescents. It is suggested that there should be targeted educational intervention program on sedentary activities, health and nutrition, students' active for physical education class time, promoting a healthy life style. Special attentions need to be given for students from high and medium income families. Parents should be role model for their children on healthy diet practice and encourage their children working regular physical activity.