Inclusion Criteria:

• Age >/= 18 years
• Histologically or cytologically documented locally advanced or metastatic UBC (including renal pelvis, ureters, urinary bladder, and urethra)
• Representative tumor specimens as specified by the protocol
• Disease progression during or following treatment with at least one platinum-containing regimen for inoperable, locally advanced or metastatic UBC or disease recurrence
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Life expectancy >/= 12 weeks
• Measurable disease, as defined by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1
• Adequate hematologic and end organ function
• For female patients of childbearing potential and male patients with partners of childbearing potential, agreement (by patient and/or partner) to use highly effective form(s) of contraception as defined by the protocol and to continue its use for 6 months after the last dose of MPDL3280A

Exclusion Criteria:

• Any approved anti-cancer therapy within 3 weeks prior to initiation of study treatment
• Treatment with any other investigational agent or participation in another clinical trial with therapeutic intent within 28 days prior to enrollment
• Active or untreated central nervous system (CNS) metastases as determined by computed tomography (CT) or magnetic resonance imaging (MRI) evaluation during screening and prior radiographic assessments
• Leptomeningeal disease
• Malignancies other than UBC within 5 years prior to Cycle 1, Day 1, with the exception of those with a negligible risk of metastasis or death and treated with expected curative outcome, or localized prostate cancer treated with curative intent and absence of prostate-specific antigen (PSA) relapse or incidental prostate cancer
• Pregnant and lactating women
• Significant cardiovascular disease
• Severe infections within 4 weeks prior to randomization
• Major surgical procedure other than for diagnosis within 4 weeks prior to randomization
• History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins; known hypersensitivity or allergy to biopharmaceuticals produced in Chinese hamster ovary cells or any component of the MPDL3280A formulation
• History of autoimmune disease
• Prior allogeneic stem cell or solid organ transplant
• History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on screening chest CT scan
• Positive test for HIV and/or active hepatitis B or hepatitis C or tuberculosis
• Administration of a live, attenuated vaccine within 4 weeks prior to randomization
• Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-CTLA-4, anti-PD-1, and anti-PD-L1 therapeutic antibodies