AbstractBackground:Along with increased prevalence of obesity, body weight misperception has also increased among adolescents. This study aims to evaluate the proportion of weight misperception among Iranian children and adolescents and its association with some health-related factors.Methods:Data were collected from 14,440 Iranian students, aged 7–18 years, who participated in the national school-based surveillance program (CASPIAN-V). The students’ anthropometric indices and blood pressure were measured using standardized methods, and valid questionnaires were used to assess their weight perception, eating patterns, physical activity and sedentary behaviors. According to agreements between the real weight and self-perceived weight status, participants were classified as underestimated, accurate and overestimated weight.Results:The rates of underestimated, accurate and overestimated weight were 30.8%, 40.8% and 28.4%, respectively. In comparison with the accurate-weight group, both the underestimated- and overestimated-weight groups were less likely to have daily consumption of sugar-sweetened beverages (OR: 0.83, 95% CI: 0.74–0.93 and OR: 0.39, 95% CI: 0.34–0.44, respectively), sweets (OR: 0.81, 95% CI: 0.73–0.90 and OR: 0.68, 95% CI: 0.61–0.76, respectively) and salty snacks (OR: 0.78, 95% CI: 0.66–0.92 and OR: 0.30, 95% CI: 0.24–0.38, respectively). In the overestimated-weight group, the odds of daily intake of fast food decreased by 67% and the odds of low physical activity declined by 38% in comparison with the accurate-weight group.Conclusions:Weight misperception had a high prevalence among Iranian children and adolescents and is associated with their dietary patterns and physical activity behaviors. Suitable education programs need to be developed to correct the children and adolescents’ insight about their weight status.