Purpose To identify the relevant factors, and create and validate a predictive scoring system for the duration of laparoscopic radical prostatectomy (LRP). Patients and Methods We retrospectively analyzed clinicopathological data from 436 patients who underwent LRP between January 2014 and January 2019, of whom 304 cases were used as a model creation group and 132 were used as a validation group. Uni/multivariate linear regression analysis was performed to determine the predictors of the duration of the procedure and a novel scoring system was created using these predictors. External validation of the scoring system was performed. The Hosmer–Lemeshow test was used to determine the goodness-of-fit of the model and calibration plots were created for visual assessment. Results “Prolonged duration” was defined as a duration of the procedure that was longer than the mean (>150 min) duration. Multivariate analysis showed that body mass index (BMI), prostate volume, intravesicular protrusion of the prostate (IPP), the ratio of the cross-sectional areas of the prostate and the Retzius space (P/R), pelvic lymph node dissection, and neurovascular bundle (NVB) preservation were significant predictors of prolonged duration. A scoring system that included these six parameters was created and the area under the curve achieved during receiver operating characteristic analysis using this scoring system was 0.874 (95% confidence interval [CI]: 0.836–0.913). The Hosmer–Lemeshow test showed that the scoring system was well calibrated (X2=5.339, P =0.376). The external validation showed that the model had high predictive accuracy (AUC=0.835, 95% CI: 0.764–0.906) and goodness-of-fit (X2=4.401, P =0.493). Conclusion The following factors were significantly associated with prolonged duration of laparoscopic radical prostatectomy: BMI, prostate volume, IPP, P/R, pelvic lymph node dissection, and NVB preservation. The novel scoring system created can be used to accurately predict the duration of the procedure, assess the difficulty of surgery, and improve perioperative efficiency.