Objective: The aim of the study was to investigate the relationship between macronutrient intake, weight status, executive functioning, and academic performance in school-aged children using a nationally representative sample. Method: Children between ages 6- and 16-years-old completed cognitive and academic portions of the third National Health and Nutrition Examination Survey (NHANES-III). Data were analyzed with ANOVAs and regression analyses, controlling for confounding variables. Results: It was found that 6–8-year-old children in the underweight range performed better than children in the overweight and obese ranges on all executive function and academic tasks. Adolescents with BMI's in the normal weight range performed better than their peers in the underweight and obese weight ranges. Of the children who reported not meeting macronutrient recommended daily allowances (RDA), those who met the RDAs performed better on executive function and academic tasks. Children in the overweight and obese weight categories reported consuming fewer total calories than their peers in the normal weight range. Demographic and socioeconomic variables were the strongest predictors of performance on both cognitive and academic variables. Higher total caloric intake contributed to Block Design performance and higher intake of carbohydrates contributed to reading and math performance. Conclusion(s): These findings suggest BMI and nutritional intake are associated with cognitive and academic performance, particularly during adolescence. The study provides support for the adverse relationship between underweight or obese weight status on cognition, executive function, and academic performance.