Purpose Older patients with colon cancer (CC) are vulnerable to chemotherapy toxicity and death. Establishing simple scores specific for patients with CC to predict severe chemotoxicity or early death is needed to select the best treatment strategy. Subjects, Materials, and Methods This prospective multicenter study included patients aged ≥70 years with CC receiving adjuvant or first‐line metastatic chemotherapy. Frailty markers (nutrition, physical activity, energy, mobility, strength), comprehensive geriatric assessment (functional status, comorbidities, falls, nutrition, cognition, and depression), and usual laboratory parameters were collected. Logistic or Cox regression was used to examine at 500 days the association between frailty markers, comprehensive geriatric assessment, laboratory parameters, and grade 3–4 toxicity or death. Results A total of 97 patients (median age, 79.0 years) received adjuvant (37.1%) or metastatic (62.9%) chemotherapy. During the first 500 days, grade 3–4 toxicity occurred in 49.5%, and 30% died. The predictive model for grade 3–4 toxicity combined (polychemotherapy × 3) + (hypoalbuminemia <32 g/L × 2) + (abnormal grip strength × 1.5) + C‐reactive protein >11 mg/L + Eastern Cooperative Oncology Group performance status (ECOG‐PS), cutoff score >3. The predictive model for death combined (metastasis × 5) + (age × 2) + alkaline phosphatase >100 IU/mL + sex (female) + abnormal grip strength + ECOG‐PS, cutoff score >6. For chemotoxicity prediction, sensitivity was 81.6% and specificity 71.4%. For death prediction, sensitivity was 89.7% and specificity was 83.6%. Conclusion These simple and efficient “ColonPrediscores” will help to better identify older patients with CC with increased risk of chemotherapy‐related toxicity and/or death. Implications for Practice The two scores assessed in this study, called “ColonPrediscores”, offer a major advantage in that they do not need a previous complete geriatric assessment, which makes them an easy‐to‐use tool in oncologic settings.