Introduction: The incidence of colorectal cancer (CRC) increases with age. In combination with an ageing population, the number of older patients undergoing surgical treatment for CRC is therefore expected to increase. Sarcopenia and cachexia are potentially modifiable risk factors of a negative surgical outcome. Sarcopenia can be categorized into primary (age-related) and secondary where diseases, such as malignancy, are influential factors. We aimed to investigate the prevalence of preoperative sarcopenia and cachexia in older (≥65 years) vulnerable patients with localized CRC. Materials and Methods: Patients included in the randomized study “Geriatric assessment and intervention in older vulnerable patients undergoing resection for colorectal cancer,” were screened for sarcopenia and cachexia prior to surgery. All patients in the present cohort were considered vulnerable with Geriatric 8 ≤ 14 points. Sarcopenia was defined according to European Guidelines (EWGSOP2), based on low muscle strength—low handgrip-strength and/or slow 5xChair-Stand-Test—and low appendicular lean mass assessed by dual-energy X-ray absorptiometry. Cachexia was defined as self-reported unintended weight loss >5% within three months or 2–5% with body mass index <20 kg/m². Results: Sixty-four patients (mean age 79.6 years ±6.4 years, 36 women) were assessed. Of these, 28% (n = 18, 11 women) had low muscle strength and 13% (n = 8, 4 women) fulfilled the criteria for sarcopenia, however, 33% (n = 21, 13 women) had low muscle mass. There was no correlation between low muscle strength and low muscle mass (r = 0.16, P = 0.22). The prevalence of cachexia was 36% (n = 23, 16 women). Low muscle mass was associated with cachexia (φ = 0.38, P = 0.005), but there was no association between sarcopenia and cachexia (φ = 0.01, P = 1.0). Discussion: Despite the included patients who fulfilled the criteria for vulnerability according to G8, relatively few (28%) had low muscle strength. Moreover, there was poor overlap between the prevalence of sarcopenia according to the EWGSOP2 guidelines (13%) and prevalence of low muscle mass (33%) in older patients with CRC. Of note also, there was no association between sarcopenia and cachexia, but an association between cachexia and low muscle mass, which highlights the importance of assessing muscle mass in patients with cancer. Trial registration: The GEPOC trial has been prospectively registered at http://clinicaltrials.gov (NCT03719573).