Background: Piperacillin/Tazobactam(Pip/Taz) is a broad-spectrum antibacterial covering aerobic, and anaerobic microorganisms. Pip/Taz plays a major role in treating sepsis, respiratory infection, and intraabdominal infection. Many studies showed inappropriate use of Pip/Taz might increase the risk of resistance. This study aimed to evaluate the appropriateness use of Pip/Taz prescribing in pediatric patients in Peidatric Intensive Care Unit (PICU) at a major tertiary hospital. Method: A retrospective and observational study was conducted to evaluate the appropriateness use of Pip/Taz in PICU. The study included all neonates and pediatrics less than 14 years old in the PICU setting who had received at least dose of Pip/Taz during their admission for the period between Jan 2020 and Jan 2021. Assessment of antimicrobial appropriateness was evaluated according to Infectious Diseases Society of America (IDSA) guidelines. Data were retrieved from the hospital’s Electronic Medical Records (EMRs) and exported to Excel spreadsheet. Results: Of 124 Pip/Taz prescriptions, 34% were inappropriate. The common indications for using Pip/Taz empirically were with sepsis and suspecting of pneumonia. The reasons for inappropriate use of Pip/Taz were due to continue using the drug based on clinical condition even the results of cultures had no growth of organisms 71%, then starting the drug without taking culture 14%, then the drug continued without justification despite culture resulted with no growth 10%, and finally continued without following sensitivity 5%. Conclusion: This study showed that there was inappropriate use of Pip/Taz at PICU. The inappropriate use was attributed to not following the lab results, culture sensitivity and not requesting microbiology culture.