Background <p>Extended surgery, including multivisceral resection, synchronous metastasectomy, and concomitant procedures for coexisting diseases, is occasionally required to achieve oncological clearance in patients with colorectal cancer. However, the perioperative and oncological impact of extended surgery in younger patients remains unclear. This study aimed to evaluate short- and long-term outcomes of extended surgery in younger patients with colorectal cancer.</p> Methods <p>We conducted a single-center retrospective study of patients aged ≤ 65 years who underwent colorectal cancer surgery between 2014 and 2023. Extended surgery was defined as multivisceral resection for locally advanced tumors, resection of synchronous metastatic lesions, or concomitant surgery for coexisting diseases. Propensity score matching was performed to compare short-term postoperative outcomes and overall survival between extended and standard surgery. A secondary analysis compared younger and elderly patients who underwent extended surgery. The primary endpoint was overall survival.</p> Results <p>After matching, 41 patients who underwent extended surgery were compared with 42 who underwent standard surgery. Extended surgery was associated with longer operative time and greater blood loss. However, rates of anastomotic leakage, major postoperative complications, and mortality were comparable between groups. Overall survival did not differ significantly between extended and standard surgery in younger patients. In addition, postoperative outcomes and overall survival were similar between younger and elderly patients undergoing extended surgery.</p> Conclusions <p>Extended surgery was associated with increased operative invasiveness but did not adversely affect perioperative outcomes or overall survival in appropriately selected younger patients with colorectal cancer. These findings suggest that extended surgery may be considered when indicated by oncological factors, irrespective of chronological age.</p>