<p>This study investigated the behavioral risk factors for noncommunicable diseases (NCDs) and their association with body weight misperception among urban Vietnamese adolescents over 3 years. The cohort comprised 457 secondary school students (mean age: 11.59 ± 0.34 at baseline, 47.4% girls) who took questionnaires and underwent anthropometric measurements. Behavioral risk scores of factors, like smoking, alcohol consumption, physical inactivity, low fruit and vegetable intake, fast food and carbonated drink consumption, and sedentary behavior, were calculated. Multivariable linear regression assessed associations with behavior risk scores as well as other regressors that modify the association between weight misperception and behavior risk scores. Physical inactivity was the most prevalent risk factor, and there was a notable increase in fast food and carbonated drink consumption, followed by sedentary behavior and alcohol consumption, during the 3-year follow-up. Almost 80% of the students exhibited at least two risk factors, and 49.3% misperceived their body weight status at baseline, with males being more inclined to underestimate but less prone to overestimate than females. Compared with those accurately perceiving their weight, higher behavioral risk scores were reported in those who underestimated their weight (β = 0.110, 95% confidence interval: 0.021–0.446, <i>p</i> &lt; 0.05). These findings underscore the rising prevalence of behavioral risk factors among Vietnamese secondary school students, emphasizing the potential benefits of school-based interventions targeting accurate body weight perception for both sexes in mitigating the risk factors for multiple NCDs.</p>