Background Colorectal cancer is primarily a condition of older adults, and surgery is the cornerstone of treatment. As life expectancy is increasing and surgical techniques and perioperative care are developing, curative surgery is often conducted even in ageing populations. However, the risk of morbidity, functional decline, and mortality following colorectal cancer resection surgery are known to increase with increasing age. This study aims to describe real-world data about postoperative mortality and morbidity after resection surgery for colorectal cancer in the elderly (>= 70 years) compared to younger patients (< 70 years), in a Swedish setting. Methods A cohort study including all patients diagnosed with colorectal cancer in a Swedish region of 1.7 million inhabitants between January 2016 and May 2020. Patients were identified through the Swedish Colorectal Cancer Registry, and all baseline and outcome variables were extracted from the registry. The following outcome measures were compared between the two age groups: 90-day mortality rates, postoperative complications, postoperative intensive care, reoperations, readmissions, and 1-year mortality. To adjust the analyses for baseline confounders in the comparison of the outcome variables, the following methods were used: marginal matching, calliper (ID matching), and logistic regression adjusted for baseline confounders. Results The cohort consisted of 5246 patients, of which 3849 (73%) underwent resection surgery. Patients that underwent resection surgery were significantly younger than those who did not (mean +/- SD, 70.9 +/- 11.4 years vs 73.7 +/- 12.8 years, p < 0.001). Multivariable analyses revealed that both 90-day and 1-year mortality rates were higher in older patients that underwent resection surgery (90-day mortality OR 2.12 [95% CI 1.26-3.59], p < 0.005). However, there were no significant differences in postoperative intensive care, postoperative complications, reoperations, or readmissions. Conclusion Elderly patients suffer increased postoperative mortality after resection surgery for colorectal cancer compared to younger individuals. Given the growing elderly population that will continue to require surgery for colorectal cancer, more efficient ways of determining and handling individual risk for older adults need to be implemented in clinical practice.