The purpose of this article is to provide an updated review of the definition, prevalence, causes, and clinical management of malnutrition in inflammatory bowel disease (IBD). Prevalence of malnutrition in IBD is estimated to be between 6.1% and 69.7% depending on the definition used, the type of IBD, the clinical setting, and whether the IBD is active or in remission. Whereas older definitions of malnutrition have been found to be correlated with mortality and length of hospital stay, the more recent European Society for Clinical Nutrition and Metabolism (ESPEN) 2015 and the Global Leadership Initiative on Malnutrition (GLIM) definitions provide significantly different prevalence estimates of malnutrition when applied to the same patient population, and further work is needed to validate these two definitions against clinical outcomes. In patients with IBD with identified malnutrition, oral nutrition supplementation, enteral nutrition, or parenteral nutrition should be started. In malnourished patients with Crohn's disease undergoing surgery, preoperative enteral nutrition has been demonstrated to reduce the rate of postoperative complications. Overall, patients with IBD are at significant risk for malnutrition and should be screened for malnutrition by using a validated screening tool. The management of malnutrition in IBD is complex, and studies are often limited in their size or their ability to demonstrate an improvement in clinical outcomes based on specific nutrition-related interventions. Future studies particularly regarding the validation of new screening tools and perioperative management of malnutrition may provide insight into the standardization of diagnosis and management of malnutrition in IBD.