Evidence reveals that gastric cancer (GC) is the fifth most common malignancy in humans, and about 770,000 people die from this cancer yearly. It has been reported that new cases and deaths from GC are more common in men than women. Therapeutic approaches, such as surgery, chemotherapy, and radiotherapy, have been common for treating GC. Nevertheless, due to the complications and limitations of these methods, researchers use novel approaches, such as immunotherapeutic or target therapies, to evaluate the effectiveness of treatment in patients with metastatic GC. Studies have shown that monotherapy is usually associated with unpromising outcomes, and combination therapy can be a more practical option for treating metastatic GC. Therefore, to clarify different aspects of chemotherapy and immunotherapy in patients with metastatic GC, this review discussed the achievements and challenges of combining immunotherapeutic methods with chemotherapeutic agents.