Lymphocele is the most common complication after pelvic lymph node dissection (PLND). Over the years, various techniques have been introduced to prevent lymphocele, but no final conclusion can be drawn regarding the superiority of one technique over another. In this prospective study, 220 patients undergoing robot-assisted radical prostatectomy between 2012 and 2015 were randomized to receive titanium clips (group A, n=110) or bipolar coagulation (group B, n=110) to seal lymphatic vessels at the level of the femoral canal during extended PLND (ePLND). Ultrasound examination was used to detect lymphoceles at 10 and 90 d after surgery. Lymphocele was defined as any clearly definable fluid collection and was considered clinically significant when requiring treatment. There were no statistically significant differences between groups A and B regarding overall lymphocele incidence (47% vs 48%; difference −0.91%, 95% confidence interval [CI] −2.6 to 0.7; p=0.9) and the rate of clinically significant lymphocele [5% vs 4%; difference 0.75%, 95% CI, 0.1–3.2; p=0.7]. The two groups were comparable regarding mean (±SD) lymphocele volume (30±32 vs 35±39ml; p=0.6), lymphocele location (unilateral, 37% vs 35%, p=0.7; bilateral, 13% vs 14%, p=0.9), and time to lymphocele diagnosis (95% vs 98% on postoperative day 10; p=0.5). In conclusion, this trial failed to identify a difference in lymphocele occurrence between clipping and coagulation of the lymphatic vessels at the level of the femoral canal during robot-assisted ePLND for prostate cancer. Patient summaryIn this study we compared the frequency of postoperative complications after sealing lymphatic vessels from the leg to the abdomen using metallic clips or electrical coagulation during robot-assisted surgery for prostate cancer. We found no difference in postoperative complications between the two methods.