Background: Equitable access to novel therapies continues to be a significant challenge in pts with mUC. We hypothesized that insurance IS could impact practice patterns and ultimately outcomes. In this multi-institution study, we investigated the impact of IS on treatment selection and OS in pts with mUC. Methods: Pts diagnosed with mUC between 2010-2023 with available outcomes and insurance data were included from two NCI-designated comprehensive cancer centers. Primary IS was used to categorize pts into three groups: Medicare, private insurance, and Medicaid/uninsured. Baseline characteristics were summarized by descriptive statistics and compared via either one-way ANOVA/Kruskal-Wallis test (continuous variables), or Pearson chi-square test/Fisher’s exact test (categorical variables). OS from time of diagnosis of mUC was calculated using the Kaplan-Meier method and compared amongst IS groups using log-rank test. Cox proportional hazards multivariable model was utilized to examine correlation of IS with OS. Results: Of the 356 pts included, 222 (62.3%) had Medicare, with 69.8% (155) having secondary coverage. Pts with private insurance or Medicaid/no insurance included 30.3% (108) and 7.3% (26) of pts respectively. As expected, pts in Medicare group had higher median age (71 yrs; range: 49-92; P<0.0001) compared to private (59; range: 31-85) or Medicaid/uninsured groups (61.0; range: 32-79) while proportion of female pts was highest in Medicaid/uninsured group (50%; P<0.0001). Race, presence of de novo mUC, smoking status, use of neoadjuvant chemotherapy, clinical trial participation, type and number of lines of therapy for mUC were not significantly different between the IS groups. Pts with Medicare had significantly higher OS (median: 44.8 mos; 95% CI: 35.3-58.5; p=0.001), compared to private insurance (28.4 mos; 95% CI, 24.3-39.2) and Medicaid/uninsured (29.9 mos; 95% CI, 16.8-44.4). Within the Medicare group, pts with secondary insurance in addition to Medicare had a trend towards better OS (50.6 mos; 95% CI, 25.3-49.5) compared to those without (36.2 mos; 95% CI, 25.3-49.5; p=0.06). On multivariable analysis adjusting for covariates such as age, histology, presence of visceral metastasis, and number of lines of therapy, private insurance (HR: 1.684, 95% CI: 1.184, 2.397; P=0.0038) and Medicaid/uninsured pts (HR: 1.84; 95% CI: 1.099-3.098; P=0.021) had significantly worse outcomes. Conclusions: Despite similar access to expertise and systemic therapy at academic centers, IS was a significant predictor of OS in pts with mUC. Pts with private insurance or Medicaid/uninsured demonstrated significantly lower OS compared to Medicare. Potential underlying drivers such as co-morbidities, access to primary care, and socioeconomic barriers could have impacted these results and warrant further examination in future studies.