Methods: This study included 509 (mean age, 54.5 years; 239 males and 270 females) patients who underwent posterior spine surgery at the department of the current study. First, clean catch urine was collected, after which a urine culture was performed for all patients before surgery. Preoperative detection of the aUTI (>105 colony-forming units/mL) rate was then determined. Subsequently, risk factors for postoperative UTI were evaluated using logistic regression analysis with the following as independent variables: age, sex, obesity, diabetes, spinal cord tumor, the preoperative Japanese Orthopedic Association (JOA) score, JOA-bladder function, preoperative urine culture positivity, aUTI, preoperative Escherichia coli detection, the postoperative catheter placement period, instrumentation, number of surgical levels, surgery duration, and blood loss. Results: The preoperative aUTI and postoperative UTI incidences were 8.1% and 4.1%, respectively. Furthermore, multivariate logistic analysis showed that the risk factor for postoperative UTI was preoperative aUTI (odds ratio, 4.234; 95% confidence interval, 1.532–11.702; p=0.005). Conclusions Preoperative aUTI is a risk factor for UTI in patients after spinal surgery.