Background & aims: CPGs propose several methods and criteria to perform nutritional assessment, a key process to determine the type and severity of malnutrition, which generates variability in clinical practice and outcomes. The aim of the study was to describe the criteria considered by clinical practice guidelines (CPGs) for nutritional assessment. Methods: We performed a scoping review systematically searching in PubMed, Trip Database, Google Scholar, and Google, until November 5, 2021. We included all CPGs mentioning tools or criteria for nutritional assessment in adults from the general population or with any specific pathology or condition. Two authors independently reviewed and decided on study selection and data extraction. Results: We included 18 CPGs (12 elaborated in Europe). The CPGs recommended heterogeneous criteria for nutritional assessment: 16/18 CPGs included at least one body composition parameter (e.g., loss of muscle mass, loss of subcutaneous fat), 15/18 included history related to dietary intake, 15/18 included clinical history (e.g., weight loss), 10/18 included anthropometric measurement (e.g., low body mass index [BMI]), 11/18 included biochemical criteria (e.g., albumin, C-reactive protein), 8/18 included physical examination (e.g., fluid retention, sarcopenia, loss of subcutaneous fat), 8/18 included functional test (e.g., decreased handgrip strength), and 1/18 included catabolic state. Also, 9/18 CPGs mentioned a tool for nutritional assessment, the Subjective Global Assessment (SGA) the most common (8/18). None of the CPGs justified the inclusion of any of the tools or criteria they mentioned. Conclusions: The CPGs mentioned heterogeneous criteria for nutritional assessment. The most commonly mentioned criteria were decreased food intake, loss of muscle mass, weight loss, and low BMI. The most mentioned tool was the SGA. None of the CPGs provided a clear rationale for using certain criteria or tools for nutritional assessment.