Background: Weight disorders are highly prevalent at the global level. Vitamin B groups are clearly involved in intracellular mechanisms, energy equation, and weight gain. The present study aims to evaluate the association of dietary vitamin B intake and obesity in a large pediatric population. Methods: This cross-sectional study was conducted among children and adolescents, aged 6-18years, living in urban and rural areas of 30 provinces of Iran. The BMI-for-age classifications were as follow: percentile <0.1, (emaciated), 0.1 ≤percentile <2.35 (thin), 2.35 ≤percentile≤84.1 (normal), 84.1 <percentile ≤97.7 (overweight), 97.1 <percentile (obese). A valid 168-item semi-quantitative Food Frequency Questionnaire (FFQ) was used to assess the usual dietary intake including vitamin B. Results: Out of 5606 children and adolescents participated (mean age: 11.62, SD: 3.32),46.8% were girls. The intake of thiamin, pyridoxine, niacin and pantothenic acid increased the likelihood of obesity, compared with the normal-weight group. Odds ratios (ORs) (95% CI) of obesity for vitamin B1, B3, B5, and B6 were 1.32 (1.14-1.53), 1.01 (1.00-1.02), 1.04 (1.00-1.08),and 1.20 (1.04-1.38), respectively. Riboﬂavin, cyanocobalamin, biotin and folic acid did not have any significant association with weight disorders (B2: OR=1.09, 95% CI =0.99-1.20); B12:OR=1.00, 95% CI=0.98-1.03; B8: OR=1.00, 95% CI=0.99-1.00 B9: OR=1.00, 95% CI=1.00-1.00). Conclusion: The current study showed a significant correlation between consumption of vitamin B group and increased risk of excess weight.