Weight-for-age, height-for-age, and weight-for-height reflect numerous nutritional status factors. Neither alone nor together, standard indicators can show the whole extent of undernutrition. The Composite Index of Anthropometric Failure (CIAF) addresses this weakness with an alternate classification approach. This study examines the extent of child undernutrition using CIAF in Yogyakarta, Indonesia, and its associated factors. This study was conducted using a cross-sectional design using Survey Status Gizi Indonesia (SSGI 2021), a national survey by including 2,877 children aged 0-59 months. Conventional indices and the CIAF were utilized to categorize child undernutrition. We applied multinomial logistic regression using STATA 15 to analyse factors associated with undernutrition among children. This study found that the rates of underweight, stunting, and wasting were 11.16 %, 17.3%, and 5.63%, respectively. The prevalence of undernutrition using CIAF was 19.95%. Factors associated with undernutrition using CIAF included older age children, higher maternal education, having five or more household members, having two or more children under five years, and lower household economic status. Thus, health providers and public health actors should consider the use of CIAF for nutritional anthropometric assessment in a wider context.