Inclusion Criteria

          -  Are participants with histologically or cytologically confirmed locally advanced or
             metastatic BTC.

          -  Availability of tumor (primary or metastatic) archival material or fresh biopsies is
             mandatory

          -  Participants with BTC must have failed or be intolerant to 1L systemic platinum-based
             chemotherapy administered for locally advanced or metastatic disease. Only one prior
             treatment line is allowed

          -  Disease must be measurable with at least 1 unidimensionally measurable lesion by
             RECIST 1.1

          -  Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) of 0 to 1

          -  Life expectancy >= 12 weeks as judged by the Investigator

          -  Adequate hematological function defined by white blood cell (WBC) count >= 3 *
             10^9/Litre with absolute neutrophil count (ANC) >= 1.5 * 109/Litre, lymphocyte count
             >= 0.5 * 10^9/Litre, platelet count >=75 * 10^9/Litre, and hemoglobin (Hgb) >= 9
             grams/decilitre

          -  Adequate hepatic function defined by a total bilirubin level =< 1.5 * upper limit of
             normal (ULN), an aspartate aminotransferase (AST) level =< 2.5 * ULN, and an alanine
             aminotransferase (ALT) level =<2.5 * ULN. For participants with liver involvement in
             their tumor, AST =< 5.0 * ULN and ALT =< 5.0 * ULN is acceptable

          -  Adequate coagulation function defined as prothrombin time (PT) or international
             normalized ratio (INR) =< 1.5 * ULN unless the participant is receiving anticoagulant
             therapy

          -  Albumin >= 3.0 grams/decilitre

          -  Hepatitis B virus (HBV) deoxyribonucleic acid (DNA) positive participants must be
             treated and on a stable dose of antivirals

          -  Adequate renal function defined by either creatinine =< 1.5 * ULN or an estimated
             creatinine clearance (CCr) > 40 milliliter (mL) per minute (min) according to the
             Cockcroft-Gault formula or by measure of CCr from 24-hour urine collection

          -  Other protocol defined inclusion criteria could apply

        Exclusion Criteria:

          -  Ampullary cancer is excluded

          -  Significant acute or chronic infections

          -  Active autoimmune disease that might deteriorate when receiving an immunostimulatory
             agent

          -  Interstitial lung disease or its history

          -  Participants who are not eligible for or have not been treated with 1L systemic
             chemotherapy

          -  Anticancer treatment within 21 days before the start of study intervention

          -  Concurrent treatment with nonpermitted drugs

          -  Prior participation in a M7824 clinical trial

          -  Prior therapy with other immunotherapy or checkpoint inhibitors, such as anti-PD 1,
             anti PD L1, anti- cytotoxic T-cell lymphocyte-4 (CTLA-4) antibodies.

          -  Pregnancy or breast feeding

          -  Systemic anticancer treatment after failing 1L platinum-based chemotherapy

          -  Other protocol defined exclusion criteria could apply