Inclusion Criteria:

   - Able to comply with the study protocol, in the investigator's judgment

   - Histologically or cytologically documented locally advanced or metastatic urothelial
   carcinoma (including renal pelvis, ureters, urinary bladder, and urethra)

   - Disease progression during or following treatment with at least one
   platinum-containing regimen (e.g., gemcitabine and cisplatin [GC], methotrexate,
   vinblastine, doxorubicin, and cisplatin [MVAC], carboplatin and gemcitabine
   [CarboGem], etc.) for inoperable locally advanced or metastatic urothelial carcinoma
   or disease recurrence

   - Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1, or 2

   - Life expectancy >/= 12 weeks

   - Adequate hematologic and end-organ function, defined by laboratory results obtained
   within 14 days prior to the first study treatment

   - For women who are not postmenopausal (>/= 12 months of non-therapy-induced amenorrhea)
   or surgically sterile (absence of ovaries and/or uterus): agreement to remain
   abstinent or use single or combined non-hormonal contraceptive methods that result in
   a failure rate of <1% per year during the treatment period and for at least 90 days
   after the last dose of study drug

Exclusion Criteria:

   - Treatment with any other investigational agent or participation in another clinical
   trial with therapeutic intent within 28 days prior to enrollment

   - Treatment with chemotherapy 14 days prior to enrollment; however, participants may be
   re-screened after the 14-day washout period

   - Treatment with radiotherapy 7 days prior to enrollment; however, participants may be
   re-screened after the 14-day washout period

   - Known primary central nervous system (CNS) malignancy or symptomatic CNS metastases

   - Pregnant or lactating, or intending to become pregnant during the study

   - Significant cardiovascular disease, such as New York Heart Association cardiac disease
   (Class II or greater), myocardial infarction within 3 months prior to randomization,
   unstable arrhythmias, or unstable angina

   - Severe infections within 4 weeks prior to enrollment, including, but not limited to,
   hospitalization for complications of infection, bacteremia, or severe pneumonia

   - Received therapeutic oral or intravenous (IV) antibiotics within 14 days prior to
   enrollment; however, participants may be re-screened after the 14-day washout period

   - Major surgical procedure within 4 weeks prior to enrollment or anticipation of need
   for a major surgical procedure during the course of the study other than for diagnosis

   - 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 atezolizumab formulation

   - Any other diseases, metabolic dysfunction, physical examination finding, or clinical
   laboratory finding giving reasonable suspicion of disease or a condition that
   contraindicates the use of the investigational drug or renders the participant at high
   risk for treatment complications

   - Participants with active hepatitis B

   - Active tuberculosis

   - Administration of a live, attenuated vaccine within 4 weeks prior to enrollment or
   anticipation that such a live, attenuated vaccine will be required during the study

   - Treatment with systemic immunostimulatory agents (including, but not limited to,
   interferons or IL-2) within 4 weeks or five half-lives of the drug, whichever is
   shorter, prior to enrollment

   - Treatment with systemic corticosteroids or other systemic immunosuppressive
   medications (including, but not limited to, prednisone, dexamethasone,
   cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis
   factor [anti-TNF] agents) within 2 weeks prior to enrollment or anticipated
   requirement for systemic immunosuppressive medications during the trial