In this Phase 2, Single-Arm, Multi-Center, Open-Label Study, participants with previously treated locally advanced unresectable or metastatic solid tumors with mismatched repair deficient (dMMR) or microsatellite instability-high (MSI-H) will be treated with anti-PD-1 Monoclonal Antibody Tislelizumab (BGB-A317).

Key Inclusion Criteria:

1. Having histological confirmed diagnosis of malignancy
2. Having locally advanced unresectable or metastatic solid tumors with MSI-H or dMMR
3. Having received prior cancer therapy regimen(s) for advanced disease.
4. At least 1 measurable lesion as defined per RECIST Version (v) 1.1
5. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1
6. Adequate organ function

Key Exclusion Criteria:

1. Prior therapy with an anti-PD-1, anti-PD-L1, anti-PD-L2 or any other antibody or drug specifically targeting T-cell co-stimulation or checkpoint pathways
2. Active leptomeningeal disease or uncontrolled brain metastasis.
3. Clinically significant pleural effusion, pericardial effusion or ascites
4. Active autoimmune diseases or history of autoimmune diseases that may relapse
5. Any active malignancy
6. Any condition that required systemic treatment with either corticosteroids (> 10 mg daily of prednisone or equivalent) or other immunosuppressive medication ≤ 14 days before the first dose of study drug
7. Having a history of interstitial lung disease, non-infectious pneumonitis, pulmonary fibrosis, acute lung diseases, or uncontrolled systemic diseases (including but not limited to diabetes, hypertension, etc.)
8. Participants with uncontrolled diabetes or uncontrolled electrolyte disorders despite standard medical management
9. Having severe chronic or active infections
10. A known history of human immunodeficiency virus infection
11. Child - Pugh B or greater cirrhosis
12. Any major surgical procedure ≤ 28 days before the first dose of study drug
13. Prior allogeneic stem cell transplantation or organ transplantation

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.