Background and Objectives: Screen time among youth has been increasingly recognized as a public health problem because of its link with obesity. This has been demonstrated in many studies conducted in developed countries but few studies have addressed the problem in developing countries, despite an increase literature about the emergence of obesity and a greater access to screen devices in a country like Vietnam. Our study aimed at assessing screen time and its relationship with BMI in adolescents of Ho Chi Minh City (HCMC), Vietnam. Methods and Study Design: In a cross-sectional study of 2024 junior high school students aged 11-14 of HCMC, students were measured for BMI and questioned on time spent watching television/Video/DVD or using computer for fun. High users were defined as time ≥2 h/d. International Obesity Task Force BMI cutoffs were used to define overweight and obesity. Results: Adolescents spent 2.2 h/d in screen time, with higher values for boys than girls (p＜0.001). 53.8% of the respondents were high users. Time spent using computers for fun increased with age, and with the household wealthy index. The overall prevalence of overweight and obesity was 21.1%. Using multiple logistic regression, overweight and obesity was higher in boys (adjusted OR=2.66, 95% CI: [2.06; 3.44], p＜0.001) and in children aged 11-12 who had a screen time ≥2 h/d (adjusted OR=1.48, 95% CI: [1.09; 1.99], p＜0.02). Conclusions: In HCMC, a majority of adolescents spent ≥2 h/d on screen time. High screen time is associated with an increased prevalence of overweight and obesity in young adolescents. Public health intervention programs are needed to reduce screen time among youth.