Introduction: The purpose of this study was to identify factors affecting the length of hospitalization of elderly patients with urinary tract infection (UTI) in an acute care hospital, where general practitioners treat the majority of them.Methods: Subjects were patients aged ≥ 65 years with UTI who were admitted to our hospital between April 2019 and March 2021. The primary endpoint was the length of hospital stay on an acute care ward. Factors associated with the primary endpoint were detected using logistic regression analysis with several explanatory variables (patients' baseline characteristics, laboratory findings, and interventions during hospitalization).Results: In total, 143 cases were eligible for analysis (88±7 years old, 37% male). Multivariate logistic regression analysis revealed that: Charlson Comorbidity Index ≥ 6, complex UTI with urologist's assessment, and the score of the Functional Oral Intake Scale (FOIS) on admission were significant factors correlated with the length of hospitalization (odds ratios: 5.07, 0.13, and 0.30, respectively).Conclusion: In older patients with UTI, CCI≥6, UTI without urologist's assessment, and a lower score of FOIS may prolong the length of stay in an acute care hospital.