Background: Open radical cystectomy (ORC) is regarded as the standard treatment for muscle-invasive bladder cancer, but robot-assisted radical cystectomy (RARC) is increasingly used in practice. A recent study showed that RARC resulted in slightly fewer minor but slightly more major complications, although the difference was not statistically significant. Some differences were found in secondary outcomes favouring either RARC or ORC. RARC use is expected to increase in coming years, which fuels the debate about whether RARC provides value for money. Objective: To assess the cost-effectiveness of RARC compared to ORC in bladder cancer. Design, setting, and participants: This economic evaluation was performed alongside a prospective multicentre comparative effectiveness study. We included 348 bladder cancer patients (ORC, n = 168; RARC, n = 180) from 19 Dutch hospitals. Outcome measurements and statistical analysis: Over 1 yr, we assessed the incremental cost per quality-adjusted life year (QALY) gained from both healthcare and societal perspectives. We used single imputation nested in the bootstrap percentile method to assess missing data and uncertainty, and inverse probability of treatment weighting to control for potential bias. Deterministic sensitivity analyses were performed to explore the impact of various parameters on the cost difference. Results and limitations: The mean healthcare cost per patient was €17 141 (95% confidence interval [CI] €15 791–€18 720) for ORC and €21 266 (95% CI €19 163–€23 650) for RARC. The mean societal cost per patient was €18 926 (95% CI €17 431–€22 642) for ORC and €24 896 (95% CI €21 925–€31 888) for RARC. On average, RARC patients gained 0.79 QALYs (95% CI 0.74–0.85) compared to 0.81 QALYs (95% CI 0.77–0.85) for ORC patients, resulting in a mean QALY difference of −0.02 (95% CI −0.05 to 0.02). Using a cost-effectiveness threshold of €80 000, RARC was cost-effective in 0.6% and 0.2% of the replications for the healthcare and societal perspectives, respectively. Conclusions: RARC shows no difference in terms of QALYs, but is more expensive than ORC. Hence, RARC does not seem to provide value for money in comparison to ORC. Patient summary: This study assessed the relation between costs and effects of robot-assisted surgery compared to open surgery for removal of the bladder in 348 Dutch patients with bladder cancer. We found that after 1 year, the two approaches were similarly effective according to a measure called quality-adjusted life years, but robot-assisted surgery was much more expensive. This trial was prospectively registered in the Netherlands Trial Register as NTR5362 (https://www.trialregister.nl/trial/5214).