Background The prevalence of obesity has increased globally, with childhood and adolescent obesity being more common in developed countries. There has been no study on teenage obesity in Bhutan. In this study, we aimed to assess the prevalence of obesity in Bhutan for the first time in order to provide a baseline for future researchers. Methods The investigation, which included 392 adolescents, aimed to identify the prevalence of overweight and obesity and its contributing factors. Anthropometric measurements, food recall and knowledge, attitude, behaviour and environment questionnaires were administered. The body mass index (BMI) cut-off points for adolescents matched with those of the US Centers for Disease Control and Prevention. Results The prevalence of overweight and obesity among the participants were 7.1% and 1.5%, respectively. The prevalence of obesity was 1.0% in females and 0.5% in males (p < 0.001). There were significant (p < 0.001) correlations between BMI and other variables; however, Pearson's χ2 test uncovered no significant associations. BMI also had no significant associations with attitude, behaviour, environment and distance travelled to school. Food recall results revealed the following findings for average food consumption: total energy intake, 3522.6 kcal; fat, 47.6 g; carbohydrate, 690.2 g; protein, 90.5 g; fibre, 20.3 g; and sodium, 12.5 g. Conclusion The results of this study clarified the prevalence of obesity among adolescents in Bhutan, who require appropriate strategies for combating overweight and obesity.