Enhanced recovery after surgery (ERAS) protocols are interdisciplinary efforts to promote better postoperative patient outcomes. This chapter will focus on the guidelines and surgery types that affect nutritional status the most. When patients are malnourished, baseline nutritional status should be improved preoperatively through nutrition supplementation. Allowing clear liquids up to 2 hours before surgery and encouraging some of those liquids to be clear carbohydrate-loading drinks have been shown to promote better patient outcomes. Patients have reduced anxiety and reduced thirst prior to surgery as well as decreased infection risk, decreased postoperative nausea and vomiting, and decreased length of hospital stay postoperatively. Optimizing blood glucose control perioperatively has also been shown to improve mortality rates and wound complications. Perioperative fluid control should be goal directed with weight monitoring to decrease complications from fluid overload. The postoperative return to oral diets should be quick to promote recovery. Immunonutrition is the use of a combination of nutrients, including arginine, glutamine, nucleotides or RNA, omega-3 fatty acids, antioxidants, and polyunsaturated long-chain fatty acids, to support nutritional status and decrease complications from surgery. There is inconclusive evidence on the effectiveness of immunonutrition across various types of patient populations, but research suggests it does no harm. Further research is needed on the benefits of the individual nutrients used in immunonutrition formulations. This comprehensive guide is designed for healthcare professionals, surgeons, and registered dietitian-nutritionists aiming to refine perioperative care, ensuring a holistic approach that integrates ERAS principles and immunonutritional strategies for the benefit of surgical patients.