Background: The rising prevalence of colorectal cancer (CRC) and chronic kidney disease (CKD) in an aging population poses challenges in the perioperative management of CRC surgery. The impact of renal function on postoperative outcomes remains controversial, with limited data available on their association with morbidity and mortality. Methods: A retrospective analysis was conducted on a high-quality, prospectively maintained CRC database from multiple hospitals in Australia. 2,286 patients who underwent CRC surgery between 2010 and 2023 were categorised based on CKD status and preoperative eGFR levels, with comprehensive data on demographics, comorbidities, surgical details, and both short-term and long-term outcomes. Multivariable logistic and Cox proportional hazards regression analyses were used to examine the associations between CKD, eGFR, and postoperative outcomes, including complications, 30-day mortality, overall survival (OS), and relapse-free survival (RFS). Results: CKD, present in 135 patients (5.9%), was independently associated with increased risk of postoperative complications, 30-day mortality, and prolonged ileus. CKD significantly reduced OS (AHR: 1.49, p<0.001) and RFS (AHR: 1.51, p<0.001), with 5-year OS and RFS rates of 58.9% and 57.4%, respectively, compared to 83.3% and 82.7% in non-CKD patients. In contrast, preoperative eGFR <60mL/min/1.73m² was significantly associated with medical complications and 30-day mortality in univariate analysis but lost significance in multivariable analysis. Conclusion: CKD is a strong predictor of increased perioperative morbidity and mortality in CRC surgery patients. Comprehensive preoperative renal function assessment is essential for optimising surgical outcomes in this population.