INTRODUCTION: Antibiotic stewardship programs (ASP) improve appropriate antibiotic use. Data are limited on the clinical benefit of ASPs in children's hospitals. This study's objective was to determine the impact of an ASP on length of stay (LOS) and readmission rate among patients admitted to children's hospitals. METHODS: Data from a prospective-audit-with-feedback ASP were used to examine the ASP review characteristics, including antibiotic(s) prescribed, clinical indication, recommendations made by the ASP, and agreement with recommendations. Propensity score analysis was utilized to determine the impact of the ASP on LOS and 30-day readmission based on whether the patient received an ASP recommendation and if the clinician agreed with recommendations. Patients were stratified on if they had a complex chronic condition status (CCC) and their service line, medical or surgical. RESULTS: Of the 8038 reviews included, 1362 (16.9%) resulted in a recommendation that was agreed with in 1116 (81%) cases. Propensity score analysis demonstrated a significantly longer LOS for the non-CCC medicine group who received an ASP recommendation (80.9 vs. 67.6 h, p < 0.001). However, for CCC medicine patients that agreed with the ASP recommendation, a clinically relevant decrease in LOS (158.1 vs. 180.3 h, p = 0.095) was observed. The 30-day readmission rate was significantly greater in CCC medicine patients when comparing those who did not receive a recommendation versus those who did receive a recommendation (7.3% vs 4.2%, respectively; p = 0.005). CONCLUSION: Children without a CCC who received an ASP recommendation had a longer length of stay. For children with CCCs, the ASP appeared to decrease LOS and significantly reduce 30-day readmission rates. Overall, this study demonstrate that ASPs offer meaningful clinical benefit justifying resource allocation needed to develop and maintain ASP programs.