Background: Malnutrition delays recovery from cancer treatment and can lead to additional serious complications. Clinical guidelines for the management of malnutrition in cancer patients are essential tools for optimizing nutritional care; therefore, their methodological quality is of great importance. This review assesses the methodological quality of international clinical guidelines for the management of malnutrition in adult cancer patients. Methods: Guidelines were identified through searches in multiple electronic databases; afterward, they were systematically reviewed with the AGREE instrument, which is one method of evaluating the methodological quality of guidelines. Results: The methodological quality of the guidelines reviewed varied greatly. The highest scores were observed in the domains "scope and purpose" and "clarity and presentation," while the lowest scores were awarded in the domains "editorial independence," "stakeholder involvement," and "applicability." Furthermore, there was consensus on the indication for parenteral nutrition and nutrition screening. However, there was a lack of consensus on how nutritional therapy should be provided. No improvement was observed in methodological quality of the more recent guidelines compared to the older ones. Conclusions: The methodological quality of clinical guidelines on malnutrition for cancer patients and the way they are reported need to be improved. To achieve this, developers should utilize available guideline assessment tools, such as the AGREE instrument, when writing or updating guidelines on this topic. © 2012 American Society for Parenteral and Enteral Nutrition.