ObjectivesTo investigate the incidence of lymphocele and determine the risk factors for postoperative lymphocele after extraperitoneal robot‐assisted radical prostatectomy by using propensity score‐matching.MethodsA total of 483 patients underwent extraperitoneal robot‐assisted radical prostatectomy for prostate cancer between January 2009 and August 2011. Of these, 200 patients underwent pelvic lymph node dissection during robot‐assisted radical prostatectomy. All patients underwent magnetic resonance imaging or computed tomography postoperatively to detect lymphocele after robot‐assisted radical prostatectomy. Propensity scores for an established control group were calculated for each patient using multivariate logistic regression based on the following covariates: age, body mass index, preoperative prostate‐specific antigen level, prostate volume calculated by transrectal ultrasound, biopsy Gleason sum and clinical tumor stage.ResultsLymphocele was identified in 41 patients (20.5%). There were no statistical differences in variables used in propensity score‐matching. Operation time, estimated blood loss, catheterization and surgical margin positivity did not show differences between the two groups. Seminal vesicle invasion (P = 0.015) and tumor volume (P = 0.042) between the two groups were significantly different. In the multivariate logistic regression model, extracapsular extension (P = 0.017, odds ratio 4.231), seminal vesicle invasion (P = 0.028, odds ratio 2.643) and the number of positive lymph nodes (P = 0.041, odds ratio 3.532) were independent risk factors for lymphocele development after extraperitoneal robot‐assisted radical prostatectomy with pelvic lymph node dissection.ConclusionsLymphocele might preferentially develop in cases with seminal vesicle invasion and large tumor volume. Additionally, extracapsular extension, seminal vesicle invasion, and the number of positive lymph nodes are independent risk factors for postoperative lymphocele after extraperitoneal robot‐assisted radical prostatectomy.