INTRODUCTION: Advances in treatment strategies for gastric and esophageal cancer have led to improved long-term outcomes, however the local and systemic effects of the primary tumor, neoadjuvant therapies and surgery, result in specific nutritional challenges. Comprehensive nutritional evaluation and support represents a core component of multidisciplinary holistic care for this patient population. AREAS COVERED: We provide a detailed overview of nutritional challenges in gastric and esophageal cancer, with a focus on malignant obstruction, preoperative optimization and survivorship. We discuss current management strategies and evidence base, and describe future therapeutic targets. EXPERT OPINION: Data to support the optimal management of malignant dysphagia and obstruction, particularly regarding patient reported outcomes, is currently lacking. The advantages of nutritional optimization in the pre- and immediate postoperative phase are well described, but further research is needed to inform optimal personalised strategies. Emerging data regarding the physiologic regulation of appetite and body weight have provided key insights and informed the development of novel therapeutic targets to improve nutritional status among patients undergoing treatment for oesophageal and gastric cancer.