Monoclonal antibodies (mAbs) have completely changed the face of oncology over the last 50 years, and they have contributed to a major breakthrough in terms of cancer therapy. Esophageal and gastric cancers, the eighth and fifth most commonly diagnosed types of cancer worldwide, respectively, have lately, been managed more effectively, with the introduction of new therapeutic treatment strategies, especially mAbs. Combination treatments and new molecules have changed the face of the disease, while more therapies are getting approved on a daily basis. This review aims to analyse the major up-to-date clinical trials using mAbs and immunotherapy for the treatment of advanced gastro-esophageal cancers.