CONTEXT: Malnutrition has a negative impact on patients with cancer. Identifying risk, nutritional status, and functional capacity can contribute to adequate and early nutritional therapy, which can reduce unfavorable clinical outcomes. OBJECTIVE: To evaluate and summarize the main instruments of nutritional assessment and functional capacity and associate their results with clinical outcomes in hospitalized patients with cancer. DATA SOURCES: A systematic search was performed in the PubMed/MEDLINE, Embase, SciELO, and LILACS databases. Studies in which researchers evaluated and compared screening, nutritional assessment, and functional capacity instruments and their associations with clinical outcomes were included. DATA EXTRACTION: The data were extracted by 2 independent reviewers. RESULTS: A total of 29 studies met the inclusion criteria (n = 20 441 individuals). The Nutritional Risk Screening-2002 (NRS-2002) and Patient-Generated Subjective Global Assessment (PG-SGA) were the most common tools used for nutritional assessment. High nutritional risk according to the NRS-2202 and worse nutritional status according to the PG-SGA and Subjective Global Assessment were positively associated with a longer hospital stay and mortality. Low functional capacity, according to handgrip strength, was associated with longer hospital stay and nutrition impact symptoms. CONCLUSIONS: Tools such as the NRS-2002, PG-SGA, Subjective Global Assessment, and handgrip strength assessment are efficacious for assessing unfavorable clinical outcomes in hospitalized patients with cancer.