In recent years, immunotherapy has become a vital part of the treatment algorithm for patients with advanced gastric cancer (AGC). Initially, immunotherapy-based regimens proved their worth in (heavily) pre-treated patients. More recently, however, immune-checkpoint inhibitors (ICIs) were also introduced in the first-line treatment of advanced gastric cancer. This article provides a brief overview of the clinical trials that form the rationale for this immunotherapy-shift in the management of gastric cancer.