Purpose Convective water vapor thermal therapy or "Rezum (TM)" treatment for lower urinary tract symptoms in men with benign prostate hypertrophy require postoperative catheterization to avoid acute urinary retention. Unsuccessful catheter removal is still unpredictable. We, therefore, aimed to identify the risk factors of failed initial trial without catheter (TWOC) after Rezum (TM) therapy inside a large cohort of patients. Methods A retrospective study was conducted on patients who underwent Rezum (TM) therapy by three referent urologists across two academic hospitals between January 2022 and January 2023. A Foley catheter was systematically placed after therapy for 7 days in all patients before TWOC. Patients characteristics [age, imagery, maximum urinary flow rate (Qmax), postvoid residual (PVR)], and treatment outcomes (International Prostate Symptom Score (IPSS), quality of life (QoL), adverse events) were analyzed at baseline and 3 months from procedure. Failed initial TWOC was defined as the incapacity to pass urine or measured PVR > 300 mL. After univariate selection, the risk factors for TWOC failure were identified using multivariate logistic regression analysis. Results 216 patients qualified for analysis with 23 (10.6%) failing the first TWOC after 7 days of catheterization. After multivariate logistic regression, only preoperative PVR predicted TWOC failure (OR 1.01; p = 0.007). The cut-off of preoperative PVR increasing this risk was 120 mL (p = 0, 02). Conclusion Over 10% of men undergoing Rezum (TM) therapy for LUTS/BPH will experience TWOC failure and AUR after 7 days of catheterization. Preoperative PVR seems to be the only independent risk factor of unsuccessful catheter removal.