Bladder cancer is one of the most common malignancies worldwide. Some studies noted sex differences in the prognosis of bladder cancer, but results are inconsistent.In this study, we assessed whether women with bladder cancer exhibit a worse prognosis, after adjustment for disease stage, age, and body mass index (BMI), using clinical data from The Cancer Genome Atlas. We used a Student's t-test to compare age and BMI in groups with different sexes.The Kaplan-Meier method with log-rank test was used to determine clinical prognosis.The BMI (30.15 vs. 26.68, P = 0.0035) and age (67.54 years vs. 66.01 years, P = 0.045) of female patients with muscle-invasive bladder cancer (MIBC) were higher than those of male patients. The overall survival (OS) prognosis of female patients was worse than that of male patients. After grouping by disease characteristics, the disease-free survival (DFS) and OS prognoses of female patients under 60 years of age were worse than those of male patients. In the group with BMI >24, the OS prognosis of female patients was worse than that of male patients, but no difference was found in DFS prognosis. In the group with BMI ≤24, the DFS prognosis of female patients was worse than that of male patients, but no difference was found in OS prognosis. Compared to males, female patients with Stage III disease demonstrated a worse DFS prognosis and poorer OS prognosis, women with stage T3 demonstrated a worse DFS prognosis, and women with stage N0 demonstrated a poorer OS prognosis. No difference was found in prognosis between male and female patients in all other groups.In patients with MIBC, women tended to exhibit a worse prognosis than men. More specifically, we found a correlation between prognosis and sex after grouping patients by BMI.