Background: In metastatic urothelial cancer (mUC), bone metastasis (BM) are associated with significant morbidity and mortality, yet their role as an independent prognostic variable remains unclear. We aimed to determine the impact of BM on overall survival (OS) in patients with mUC treated with first-line platinum-based chemotherapy (PBC). Methods: mUC patients receiving PBC at the Princess Margaret Cancer Center, Tom Baker Cancer Center, or Cross Cancer Institute from January 2005 to January 2018 were identified retrospectively using central pharmacy database records. Patient disease, treatment, and response characteristics were collected. Progression-free survival (PFS) and OS were estimated using the Kaplan–Meier method. Variables reaching significance ( p < 0.05) in univariable analysis (UVA) of survival (OS) were included in multivariable analysis (MVA) (Cox). Results: Overall, 376 patients with a median follow-up of 16.8 (range: 2.2–218.3) months were included. Median age was 67 (range: 28–91) years, 76% were male, 63% had an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0–1, and 41% had BM. All patients received first-line PBC. Patients with BM had inferior median PFS (4.9 months (95% CI 3.6–6.2) versus 6.5 months (95% CI 5.4–7.6), p = 0.03) and median OS (8.8 months (95% CI 7.8–9.7) versus 10.8 months (95% CI 9.1–12.5), p = 0.002). In UVA, ECOG PS 2–3 ( p < 0.001), presence of BM ( p = 0.002), and WBC count ⩾ 11,000 cells/mm³ ( p = 0.001) were associated with inferior survival. Prior cystectomy ( p < 0.001) and lack of progression (stable disease, partial or complete response) on treatment was associated with improved OS ( p < 0.001). These variables maintained significance in MVA. Conclusion: In this retrospective study, mUC patients with BM had worse OS suggesting that BM may be an independent negative prognostic factor and including BM as a stratification factor in future mUC clinical trial designs may be warranted. A greater focus must be placed on novel therapeutic strategies to better manage BM to reduce both morbidity and mortality.