Background: Earlier studies on the cost of muscle-invasive bladder cancer treatments lack granularity and are limited to 180 days. The objective of this study is to compare the one-year costs associated with trimodal therapy versus radical cystectomy, accounting for survival and intensity effects on total costs. Methods: This cohort study used the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. Data analysis was performed from March 5, 2018 through December 4, 2018. A total of 2,963 patients aged 66-85 years diagnosed with clinical stage T2-4a muscle-invasive bladder cancer from January 1, 2002 through December 31, 2011. Total Medicare costs within one year of diagnosis following radical cystectomy versus trimodal therapy were compared using inverse probability of treatment-weighted (IPTW) propensity score models, which included a two-part estimator to account for intrinsic selection bias. Results: Median costs were significantly higher for trimodal therapy than radical cystectomy in 90 days ($83,754 vs. $68,692; median difference $11,805, 95% CI $7,745 to $15,864), 180 days ($187,162 vs. $109,078; median difference $62,370, 95% CI $55,581 to $69,160), and 365 days ($289,142 vs. $148,757; median difference $109,027, 95% CI $98,692 to $119,363), respectively. Outpatient care, radiology, medication expenses and pathology/laboratory costs contributed largely to the higher costs associated with trimodal therapy. On IPTW-adjusted analyses, patients undergoing trimodal therapy had $129,854 (95% CI $115,793-$145,299) higher costs compared with radical cystectomy one year after diagnosis. Conclusions: Compared to radical cystectomy, trimodal therapy was associated with higher costs among patients with muscle-invasive bladder cancer. Extrapolating cost figures resulted in nationwide excess spending of $444 million for trimodal therapy compared with radical cystectomy for patients diagnosed in 2017.