Malnutrition is a leading cause of morbidity and mortality, especially among older adults. However, diagnosis and treatment of malnutrition in the hospital setting are often overlooked. In recent years, quality improvement (QI) initiatives to increase the assessment and treatment of malnutrition in hospital settings have been implemented and shown to improve both patient health and economic outcomes. The Malnutrition Quality Improvement Initiative (MQii) Toolkit was designed in an effort to support hospitals seeking to implement malnutrition QI initiatives. The Toolkit has been implemented, studied, and updated for optimization of content, adaptability, and usability over several cycles of improvement from 2016-2017 at more than 50 hospital centers in the United States. The result is an open access, customizable, and user-friendly MQii Toolkit that can facilitate the implementation of malnutrition QI initiatives in individual facilities. This article introduces the MQii Toolkit, describes the process by which it was designed and improved, and orients clinical care teams to its use.