Aim: Identification of the risks of postoperative complications may be challenging in older patients with heterogeneous physical and cognitive status. The aim of this multicentre, observational study was to identify variables that affect the outcomes of colon cancer surgery and, especially, to find tools to quantify the risks related to surgery. Method: Patients aged ≥80 years with electively operated Stage I–III colon cancer were recruited. The prospectively collected data included comorbidities, results of the onco-geriatric screening tool (G8), Clinical Frailty Scale (CFS), Charlson Comorbidity Index (CCI) and Mini Nutritional Assessment-Short Form (MNA-SF), and operative and postoperative outcomes. Results: A total of 161 patients (mean 84.5 years, range 80–97, 60% female) were included. History of cerebral stroke (64% vs. 37%, p = 0.02), albumin level 31–34 g/l compared with ≥35 g/l (57% vs. 32%, p = 0.007), CFS 3–4 and 5–9 compared with CFS 1–2 (49% and 47% vs. 16%, respectively) and American Society of Anesthesiologists score >3 (77% vs. 28%, P = 0.006) were related to a higher risk of complications. In multivariate logistic regression analysis CFS ≥3 (OR 6.06, 95% CI 1.88–19.5, p = 0.003) and albumin level 31–34 g/l (OR 3.88, 1.61–9.38, p = 0.003) were significantly associated with postoperative complications. Severe complications were more common in patients with chronic obstructive pulmonary disease (43% vs. 13%, p = 0.047), renal failure (25% vs. 12%, p = 0.021), albumin level 31–34 g/l (26% vs. 8%, p = 0.014) and CCI >6 (23% vs. 10%, p = 0.034). Conclusion: Surgery on physically and cognitively fit aged colon cancer patients with CFS 1–2 can lead to excellent operative outcomes similar to those of younger patients. The CFS could be a useful screening tool for predicting postoperative complications.