This study aimed to assess the relationship between the Dietary Inflammatory Index (DII®), a validated tool for evaluating diet-associated inflammation, and anthropometric indices in children and adolescents. This multicentre survey was conducted on 5427 school students selected via multistage cluster sampling from thirty provinces of Iran. This survey was conducted under the framework of the weight disorders survey, which is part of a national surveillance programme entitled Childhood and Adolescence Surveillance and Prevention of Adult Non-communicable Diseases-IV. For calculating the DII scores, twenty-five dietary factors were obtained from a validated 168-item FFQ. Height, weight, wrist circumference, neck circumference (NC), waist circumference (WC) and hip circumference (HC) were measured. BMI z-score, waist circumference:hip circumference ratio (WHR), waist circumference:height ratio (WHtR) and parental BMI were computed. Linear regression models were used to evaluate the association of DII and anthropometric indices. Significant trends were observed across quartiles of DII score for all anthropometric indices in all participants (P <0·05), except for WHR and WHtR. After adjustment for potential confounders, the multiple linear regression analysis for each anthropometric index revealed that participants in the highest DII quartile had higher BMI z-score, WC, HC and parental BMI compared with those in the first (or lowest) quartile. In summary, we found that a pro-inflammatory diet was associated with higher BMI z-score, wrist circumference, NC, WC, HC and parental BMI. The large sample size of the present study may influence the statistical significance of observed associations. Hence, the findings should be clinically interpreted with caution.