Background The decision to lose weight among adolescents is complex and is guided by a number of body‐related factors. This study examined the extent of agreement between actual weight, measured as body mass index, and self‐perceived weight and assessed their relative importance in weight loss behaviour among Lebanese adolescents. Methods Data on 278 adolescents aged 13–17 years were drawn from the nationwide Nutrition and Non‐Communicable Disease Risk Factor Survey (Lebanon, 2009). Binary multivariable logistic regressions were conducted to test associations with “effort to lose weight” as the outcome variable, controlling for a number of potential confounders. Results Close to 36% reported trying to lose weight. Around 21% and 13% were overweight and obese, respectively, and 40% and 10% perceived their weight as slightly high and very high, respectively. Inaccurate perceivers, those underestimating or overestimating their weight, constituted 39%, with overall percent agreement between actual and self‐perceived weight being 60.8% (kappa statistic = 0.319, 95% CI [0.242, 0.396]). About a third of the overweight adolescents (30.5%) and more than half of the obese (56.8%) underestimated their weight. In the multivariable analysis, self‐perceived weight was statistically significant and a stronger predictor of weight loss effort than body mass index (adjusted odds ratios = 14.42 and 6.42 for slightly high and very high perceived weight, respectively, compared to odds ratios = 1.47 and 2.31 for overweight and obese adolescents, respectively). Conclusion Health professionals need to consider self‐perceived weight in conjunction with actual weight in their pursuit of weight management goals and in planning prevention programmes that guide weight loss behaviours for adolescents.