Background: The prevalence of stunting, thinness, overweight, and obesity among children differs by ethnicity. It is not known whether differences in body build across the ethnic groups influence the interpretation of nutritional parameters. Objective: To explore the differences in body build across the 5 main ethnic groups in Malaysia and to determine whether differences in body build have an impact on the interpretation of nutrition indicators. Methods: A total of 3227 children aged 2.0 to 12.9 years who participated in the South East Asian Nutrition Surveys (SEANUTS) in Malaysia were included in this analysis. Body weight, height, sitting height, wrist and knee breadths, and biceps and subscapular skinfolds were measured, and relative leg length, slenderness index, and sum of skinfolds were calculated. Z scores for height-for-age (HAZ) and body mass index-for-age (BAZ) were calculated using the World Health Organization (WHO) 2007 growth standards. Results: Differences in relative leg length and slenderness across the ethnic groups were correlated with HAZ and BAZ. Correction for differences in body build did, in some ethnic groups, have significant impact on the prevalence of stunting, thinness, overweight, and obesity, and the pattern of prevalence across ethnic groups changed. Conclusion: At the population level, corrections for body build had only minor and mostly nonsignificant effects on prevalence, but at an individual level, corrections for body build placed a substantial number of children in different height or weight categories. Whether these misclassifications warrant additional assessment of body build in clinical practice will need further investigation.