Purpose: Antibiotics play an important role in reducing child mortality due to pneumonia. Ineffectiveness in prescribing and using antibiotics will lead to many inappropriate prescribing and inappropriate use of antibiotics that will affect the irrational use of antibiotics in patients. The irrationality of antibiotics for death and length of stay has not been done much.Methodology: This research was an observational research with the cross sectional approach. The population of this study was every pneumonia pediatric patients who were hospitalized in one hospital in Central Java in the inpatient ward or PICU. The sampling technique used is Nonprobability sampling technique with purposive sampling method. Secondary data were obtained from medical records. Chi-square tests and logistic regression were used to process the data.Results: The use of antibiotics according to the Gyssens flow evaluation obtained the results of irrational antibiotics most used in category IV A as many as 70 patients (72.2%), in category IV C as much as (3.1%), and rational antibiotics in category 0 as many as 24 patients (24.7%). The mortality outcome for pneumonia pediatric patients was 6 patients (6.2%) and 91 patients (93.8%) went home. There are 74 pneumonia pediatric in-patients (76.3%) with 0-7 days hospitalization period and 23 pneumonia pediatric in-patients (23.7%) with > 7 days hospitalization period.