Background: Pneumonia is a leading cause of death in infants and children. Pneumonia accounts for 15% of all causes of death of children under the age of 5 years, and is estimated to kill about 920,136 children under the age of 5 in 2015. Common treatmentused to treat pneumonia is by administering antibiotics. Inappropriate use of antibiotics can lead to less effective treatment, increased resistance, decreased drug safety and high cost of care due to the length of stay in hospital. Objective: To analyze the relationship of the rationality of antibiotic use to the outcome of death and length of stay of pediatric patients with pneumonia in private hospitals in Surakarta. Research Methods: This study was an observational study with a cross sectional approach. The study population was all pneumonia patients in children who were hospitalized in private hospitals in Surakarta in the inpatient ward and PICU room during the period 2014 - 2018. The sampling technique used was Non probability sampling technique with purposive sampling method. Data collection used secondary data obtained from patient history based on medical records for the period October 2014 - October 2018, patient identity and objective data. The method used in processing data was Chi Square analysis. Multivariate analysis was performed with a multiple logistic regression test. Results: There is no relationship between sex, length of stay and use of antibiotics with death outcomes in pediatric patients with pneumonia. There is a relationship with age with mortality outcomes in pediatric patients with pneumonia. There is no relationship between sex, age, and outcome of death with length of stay in pediatric patients with pneumonia. There is a relationship between the rationality of antibiotic use and the length of stay in pediatric patients with pneumonia. Overall there is no relationship between sex, age, and use of antibiotics with inpatient mortality outcomes in pediatric patients with pneumonia. The most dominant variable associated with length of stay in pediatric patients with pneumonia is the use of antibiotics with p = 0.045 and Exp (B) = 4.952; Cl = 1,034-23,722. Conclusion: The rationality of antibiotic use on mortality outcomes do not show a significant relationship, but the rationality of antibiotic use was related to length of stay.