Background: The association of duration of breastfeeding (BF) with weight disorders remains controversial. This study aimed to evaluate the association of BF with anthropometric measures and weight disorders in Iranian children and adolescents. Materials and Methods: Using multistage random cluster sampling method, a representative sample of 25,000 school students were selected from urban and rural areas of 30 provinces of Iran
(2011-2012). Through a validated questionnaire, data was recorded for every participant. Anthropometricand measures and duration of BF were measured under international standard protocols by using calibrated instruments. Results: Overall, 23,043 students completed the survey (participation rate: 92.17%). They consisted of 50.8% boys, 73.4% urban residents, with a mean age of 12.55 ± 3.31 years. Significant association was found between BF duration and overweight (P<0.05). In multivariate model, longer duration of BF (BF ≥ 6 months versus < 6 months), was associated with lower risk of becoming overweight [odds ratio(OR):0.86(0.74,0.99)]. There was no significant association between duration of BF with body mass index(BMI), waist circumference, hip circumference, neck circumference, wrist circumference, generalized obesity and abdominal obesity. Conclusion: Although the longer duration of BF is associated with lower risk of becoming overweight, does not seem to be associated with anthropometric measures in childhood and adolescence. To confirm the results of the present study, more longitudinal studies in Iranian children and adolescents are warranted.