Background: Bladder preservation with trimodal therapy (TMT), which consists of maximal transurethral resection of bladder tumors followed by chemoradiation, is now included in guidelines with radical cystectomy (RC) as options for definitive management of muscle-invasive bladder cancer (MIBC). Prospective randomized controlled trial data to help guide treatment selection are lacking, and prior efforts to bridge this knowledge gap have failed primarily due to poor accrual. A recent retrospective analysis comparing TMT to RC reported similar oncologic outcomes between these treatments when performed in highly selected patients. However, treatment toxicities and costs vary significantly between these management options. To investigate the impact of these outcomes on relative treatment value, we evaluated the comparative cost-effectiveness of TMT and RC for treatment of MIBC. Methods: Cost-effectiveness was compared between TMT and RC for patients with a solitary, muscle-invasive tumor less than 7cm, no or unilateral hydronephrosis, limited carcinoma in situ, and adequate bladder function (criteria utilized in a recent retrospective comparative series) using a microsimulation model with a 5-year horizon from a Medicare payer perspective. Additionally, a 10-year lifetime horizon was evaluated to better understand the impact of long-term outcome uncertainty on cost-effectiveness. Based on recently published multicenter retrospective propensity score matched data, metastatic progression and survival probabilities were assumed to be equivalent between treatments. Utility values and additional probabilities, including both short and long-term treatment toxicities, were obtained from published literature. Primary outcomes of interest included effectiveness measured in quality adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICER) using a willingness-to-pay threshold of $100,000/QALY. One-way and probabilistic sensitivity analyses were performed to assess the robustness of the model. Results: At 5 years, the average cost was $32,286.35 higher for TMT versus RC. The average QALYs were 3.88 and 3.96 for RC and TMT respectively. TMT was not cost-effective at 5-year (ICER: $379,917.21/QALY) or 10-year (ICER: $222,704.78/QALY) time horizons. On one-way sensitivity analyses, TMT would become cost effective if: 1) TMT costs were less than $16,152; or 2) TMT resulted in a 13.3% improvement in metastasis free survival relative to RC. Conclusions: Although it resulted in similar quality and duration of life, TMT was not cost-effective relative to RC at 5 and 10 years given higher treatment costs. These findings support the role of both TMT and RC in management of MIBC and highlight the need for continued efforts to reduce healthcare costs associated with TMT.