Background: Sarcopenia has gained considerable recognition as an important prognostic factor for complications, longer hospital stay, and survival following cystectomy for bladder cancer. However, inconsistent cutoff values to define sarcopenia have been utilized throughout the literature. Our aim was to evaluate sarcopenia as a predictor of outcomes following radical cystectomy with urinary diversion (RCUD) using the international consensus definition, Martin criteria, and Mayr criteria, as a standardized cutoff value would potentially reduce bias across studies. Methods: A retrospective analysis of patients treated with RCUD at our institution between 2010 and 2017 was performed. Sarcopenia was defined according to the aforementioned criteria and assessed by measuring total psoas area (TPA) on preoperative computerized tomography. The impact of sarcopenia on perioperative outcomes, cancer-specific survival (CSS), and overall survival (OS) was evaluated with univariate and multivariate regression models. Results: Of 258 patients who underwent RCUD, 195 had available computed tomography scans within 90 days of surgery. The median TPA scores among men and women were 578.0 and 459.6 mm²/mm², respectively. The overall incidence of sarcopenia according to the international consensus definition, Martin criteria, and Mayr criteria was 36.4% (71/195), 24.1% (47/195), and 31.3% (61/195), respectively. Regardless of definition, significant differences were not observed in length of stay, high grade complications, readmissions, and discharge destination (all P> .05). Furthermore, sarcopenia was not significantly associated with CSS or OS. The median follow-up time was 4.1 years (95% CI: 3.6 - 4.4). The 5-year CSS and OS were 46.3% and 66.2%, respectively. Conclusions: Irrespective of definition, we were unable to externally validate sarcopenia as a predictor of perioperative outcomes in our contemporary cohort. Future studies will evaluate the impact of our evolving perioperative care pathway on oncological outcomes, including its ability to mitigate the effects of sarcopenia through reducing the physiological and mental demands of surgery.