Background: Nutritional status in children is an indicator to find out whether a child is are stunted, wasted or severely wasted, or are underweight or severely underweight underweight. Undernutrition in critically ill patients aged 0 – 5 years is closely related with mortality. Due to other disease factors that exist in critically ill patients thereby inhibiting childrens growth and reducing the quality of life in children with undernutrition. Although various ways are taken to improve nutritional status in children aged 0 – 5 years, the incidence of mortality remains with malnutrition in Indonesia remains high. The aim of this research is to find out. The relationship between undernutrition in critically ill patients and mortality at the Pediatric Intensive Care Unit (PICU) as well as a means of increasing knowledge between malnutrition and mortality. Providing nutrition to critically ill patients with undernutrition is very important to prevent even more severe undernutrition. Undernutrition in critically ill patients, especially in children aged 0–5 years, will affect the childs future growth and development. And intensive care in the PICU can also influence the high mortality rate in children aged 0-5 years.