Undernutrition in hospitalized older adults is increasingly being recognized as a serious problem with implications for both patient care and outcomes and health service utilization and costs. This article presents an overview of research that has been conducted examining undernutrition in hospitalized older adults. First, findings from observational studies examining patterns and predictors of undernutrition in hospitalized older adults will be described, with a focus on methodological challenges. Second, clinical outcomes and costs associated with undernutrition in hospitalized older adults will be presented, both while in the hospital and subsequent to discharge. Third, a description of interventions that have already been implemented in hospitalized older adults will be described. Finally, future areas of inquiry and opportunities for evidence-based nutritional interventions targeted at older adults during and following hospitalization will be suggested. The emphasis of the discussion on interventions will focus on processes of care and the hospital environment. © Taylor & Francis Group, LLC.