Background Due to increasing healthcare costs, discussions regarding increased hospital costs when operating on high-risk patients is rising. Therefore, the aim of this study was to analyze if oldest-old colorectal cancer patients have a greater impact on hospital costs than their younger counterparts. Methods: All colorectal cancer procedures performed in 29 Dutch hospitals between 2010 and 2012 and listed in the Dutch Surgical Colorectal Audit were analyzed. Oldest-old patients (≥85 years) were compared to patients <85 years. Ninety-day hospital costs were measured uniformly in all hospitals based on time-driven activity-based costs. Results: Compared to <85-year-old patients (n = 9130), the oldest old (n = 783) had longer hospital stays (LOS) (11.3 vs. 13.2, P < 0.001), more severe complications (21.8% vs. 29.0%, P < 0.001), more failure to rescue (13.9% vs. 37.0%, P < 0.001) and higher mortality (3.0% vs. 10.7%, P < 0.001). Deceased oldest-old patients had significantly less LOS and less LOS ICU. Total hospital costs were 3% lower for oldest-old patients (€13,168) than for <85-year-old patients (€13,644, P < 0.001). In cases of severe complications or death, hospital costs for the oldest old were 25% and 31% lower than those of <85-year-old patients (both P < 0.001). Conclusion: Although frequently assumed to be more expensive, operating on oldest-old patients with colorectal cancer does not increase hospital costs compared to younger patients. This was most likely due to faster deterioration or less aggressive treatment of oldest-old patients when (severe) complications occurred. J. Surg. Oncol. 2016;114:1009–1015.