Introduction malnutrition is a common problem in Ethiopia. Studies show malnourished children in intensive care units succumb more often to infection and death but Ethiopia has no available data to assess the prevalence of malnutrition in children admitted to pediatric Intensive Care Unit and their clinical patterns, this study was conducted to assess these variables in a tertiary hospital in Ethiopia. Methods this was a retrospective cross sectional study done on 243 children, ranging from 1 month to 15 years of age, from January 2016 to December 2018. Anthropometric interpretation was done using WHO Z score charts. The assessed outcome variables were death, length of stay in pediatric intensive care unit (PICU), days on mechanical ventilator and hospital acquired infection. Collected data was entered and analyzed using SPSS 20.0 version. Results the overall prevalence of wasting was 37.8% (n=92). Stunting was seen in 45.7% (n=111). Compared to well-nourished children, malnourished children were more likely to require mechanical ventilation (78.3% versus 66.2% OR-2, p=0.045), experience longer time on mechanical ventilation (10.3±13.2 days versus 6.1±7.9 days, p=0.012), develop hospital acquired infection (HAI) more often (30.4% versus 19.2%, p=0.045), and have a prolonged length of stay (10.7±16.4 days versus 6.1±8.4 days, p=0.005). Conclusion malnutrition in our PICU was identified to be a common cause of morbidity associated with greater need for mechanical ventilation, prolonged ventilator days, increased HAI, and longer hospital stays. Taking into consideration scarcity of resources, malnutrition imposes great burden on clinical care.