OBJECTIVE: Colorectal cancer is the third most diagnosed malignant neoplasm in the world and the fourth leading cause of cancer mortality. The loss of muscle mass in oncological patients is the main aspect of cancer-related malnutrition. Associations between sarcopenia and poor outcomes, such as high postoperative mortality, chemotherapy toxicity, and reduced survival, have been recently described. The aim of this study was to prospectively assess the prevalence of preoperative sarcopenia in patients with colorectal cancer using validated methods to evaluate muscle strength, muscle mass, and physical performance. METHODOLOGY: This study included patients with colorectal cancer undergoing oncological staging at a Cancer Center in Brazil from May 2019 to March 2020 who had images from abdominal computed tomography available for analysis of body composition. The muscle strength test, physical performance, referred fatigue, and clinical and nutritional data were evaluated. RESULTS: A total of 31 patients were included, and most were diagnosed with colon cancer (77.4%) and clinical stage II in 41.9% of cases. The prevalence of probable sarcopenia was 22.6%; of these patients, sarcopenia was confirmed in 19.4%, and ultimately, 9.7% of the sample was classified as severe sarcopenia. We did not find a significant association between the presence of sarcopenia in our sample and age, sex, tumor staging, nutritional characteristics, referred patient fatigue, or postoperative complications. CONCLUSION: Considering the criteria established by the EWGSOP, the prevalence of preoperative sarcopenia in colorectal cancer patients was 19.4%.