Gastric cancer treatments are rapidly evolving, leading to significant survival benefit. Recent evidence provided by clinical trials strongly encouraged the use of perioperative chemotherapy as standard treatment for the localized disease, whereas in the advanced disease setting, molecular characterization has improved patients’ selection for tailored therapeutic approaches, including molecular targeted therapy and immunotherapy. The role of nutritional therapy is widely recognized, with oncologic treatment’s tolerance and response being better in well-nourished patients. In this review, literature data on strategies or nutritional interventions will be critically examined, with particular regard to different treatment phases (perioperative, metastatic, and palliative settings), with the aim to draw practical indications for an adequate nutritional support of gastric cancer patients and provide an insight on future directions in nutritional strategies. We extensively analyzed the last 10 years of literature, in order to provide evidence that may fit current clinical practice both in terms of nutritional interventions and oncological treatment. Overall, 137 works were selected: 34 Randomized Clinical Trials (RCTs), 12 meta-analysis, 9 reviews, and the most relevant prospective, retrospective and cross-sectional studies in this setting. Eleven ongoing trials have been selected from clinicaltrial.gov as representative of current research. One limitation of our work lies in the heterogeneity of the described studies, in terms of sample size, study procedures, and both nutritional and clinical outcomes. Indeed, to date, there are no specific evidence-based guidelines in this fields, therefore we proposed a clinical algorithm with the aim to indicate an appropriate nutritional strategy for gastric cancer patients.