We aimed to investigate the association between nutrition and blood pressure and the role that body composition plays in this relationship. Korea National Health and Nutrition Examination Survey data from the years 2008–2020 were reviewed. A total of 11,234 subjects (5974 boys and 5260 girls) aged 10–18 years of age were selected. We analyzed the correlation between nutrition (intakes of energy, protein, fat, carbohydrate, sodium, saturated fatty acid (SFA), unsaturated fatty acid (USFA), and dietary fiber (DF)) and body composition (height, weight, waist circumference (WC), body mass index (BMI), and waist to height ratio (WHtR)), and performed multiple regression analysis to find the independent correlation between body composition and blood pressure (BP). We then compared the correlation between nutrition and BP, with or without adjustment for body composition. The intakes of energy, protein, fat, carbohydrate, sodium, and USFA had positive associations with height, weight, WC, and BMI. Systolic BP (SBP) and diastolic BP (DBP) were independently positively correlated with height and BMI. The intakes of energy, protein, fat, carbohydrate, sodium, and SFA had positive correlations with SBP and DBP, which disappeared when additionally adjusted for BMI and height. In conclusion, nutrition seems to affect BP via height and BMI in Korean children and adolescents.