Background: Radical cystectomy with pelvic lymph node dissection (PLND) and urinary diversion in patients with bladder cancer is known for its high risk of complications. Although open radical cystectomy (ORC) is regarded as the standard treatment, robot-assisted radical cystectomy (RARC) is increasingly used in practice, despite the fact that high-quality evidence comparing the effectiveness of both techniques is lacking. Objective: To study the effectiveness of RARC compared with that of ORC, in terms of 90 d complications (Clavien-Dindo), health-related quality of life (HRQOL), and clinical outcomes. Design, setting, and participants: A prospective comparative effectiveness study was conducted in 19 Dutch centres, expert in either ORC or RARC. Follow-up visits were scheduled at 30, 90, and 365 d. Intervention: Standard ORC or RARC with PLND, using a standardised perioperative protocol. Outcome measurements and statistical analysis: The primary outcome was any-grade complications after 90 d. Secondary outcomes included HRQOL, complications (minor, major, 30 d, and 365 d), and clinical outcomes. Differences were calculated as risk differences (RDs) between the groups with 95% confidence intervals (CIs), adjusted for potential baseline differences by means of propensity score–based inverse probability of treatment weighting. Results and limitations: Between March 2016 and November 2018, 348 patients were included (n = 168 for ORC, n = 180 for RARC). At 90 d, any-grade complication rates were 63% for ORC and 56% for RARC (RD –6.4%, 95% CI –17 to 4.5). Major complication rates were 15% for ORC and 16% for RARC (RD 0.9%, 95% CI –7.0 to 8.8). Total minor complication rates were 57% for ORC and 49% for RARC (RD –7.6%, 95% CI –19 to 3.6). Analyses showed no statistically significant differences in HRQOL between ORC and RARC. Some differences were found in the secondary outcomes in favour of either RARC or ORC. The major drawback inherent to the design comprises residual confounding. Conclusions: This multicentre comparative effectiveness study showed no statistically significant differences between ORC and RARC in terms of complications and HRQOL. Patient summary: This multicentre study did not show differences in overall complication rates, health-related quality of life, mortality, and clinical and oncological outcomes between open and robot-assisted radical cystectomy in bladder cancer patients.