Purpose: Some patients who undergo robot-assisted laparoscopic radical prostatectomy (RARP) continue to experience long-term urinary incontinence (UI). This study aimed to evaluate easily obtainable factors that can predict long-term UI following RARP. Materials and Methods: A total of 315 patients who underwent RARP for localized prostatic cancer were analyzed. We separated the patients into two groups, namely, the Continence group and the Incontinence group, according to the presence or absence of UI at 12 months after surgery, and we compared the patients’ characteristics and operative data to identify clinical signs associated with long-term UI. Additionally, correlations between these factors and postoperative urethral function were evaluated. Urinary continence was defined as both the use of 0 pads/per day and <2 g of urine lost using the 24-h pad weight test. Results: Of 315 patients, 250 (79.4%) achieved urinary continence and 65 (20.6%) had UI. Age, storage-related lower urinary tract symptoms before surgery, nerve-sparing surgery, and the 24-h urine loss immediately after urethral catheter removal significantly affected long-term UI after RARP. Multivariate logistic regression analyses revealed that the 24-h urine loss after catheter removal was a significant predictor of long-term UI. Receiver operating characteristic curve analysis identified a urine loss of 330 g/day as the optimal cutoff value, which yielded 92% sensitivity and 84% specificity, and it showed significant correlations with postoperative urethral function and the time to recover urinary continence. Conclusion: The 24-h urine loss immediately after urethral catheter removal may be the most reliable and useful predictor of long-term UI following RARP.