Colorectal cancer is one of the most common malignancies in China and worldwide. Neoadjuvant radiochemotherapy has inspiring therapeutic effect in treating colorectal cancer with high risk of recurrence. However, malnutrition is prevalent in patients with colorectal cancer and causes clinical deterioration. To investigate the impact of neoadjuvant radiochemotherapy on the nutritional status of colorectal cancer patients, we interviewed 310 colorectal cancer patients, collected information, and analysed the relationship between risk factors, Adverse Events (AEs), and nutritional status using the screening tool of NRS2002. The results showed that patients in nutritional risk increased from 83.9% to 92.2% after anti-cancer therapy. In addition, the one identified as undernourished increased from 15.2% to 19.6% during the same period. Importantly, the nutritional risk was estimated to exist in 86.9% of patients older than 65 years, which is significantly lower in younger patients (80.9%). Additionally, constipation, diarrhoea, and oedema/ascites were the leading symptoms jeopardizing colorectal patients’ nutritional status. Patients identified as being at risk at the first-admission assessment had a higher incidence of anticancer therapy-related AEs compared with no-risk patients. In conclusion, considerable patients with colorectal cancer were in poor nutritional status before and after neoadjuvant therapy. Comprehensive nutritional assessment and appropriate nutritional intervention is necessary in the treatment of colorectal cancer.