Several Phase II studies have demonstrated the feasibility, effectiveness, and good tolerability of neoadjuvant immune checkpoint inhibitor (ICI) treatment for localized dMMR colorectal and rectal cancers. The significant clinical and pathological complete response rates offer the possibility of avoiding surgical resection. dMMR colorectal cancers are generally larger and more advanced than pMMR tumors, often requiring more extensive surgery with associated risks such as anastomotic leakage, ureteral injury, and infection. If oncological outcomes are not affected (requiring long-term follow-up), non-surgical treatment becomes an attractive option for localized dMMR colorectal cancer. Moreover, pelvic radiotherapy, the standard for locally advanced rectal cancer, causes both short-term and long-term adverse effects (e.g., bowel and bladder dysfunction, fistula, infertility), significantly impacting quality of life. Total mesorectal excision also carries risks of complications and sexual dysfunction, often requiring a stoma, making organ preservation a more urgent need for rectal cancer patients. Phase II trials and the international watch-and-wait database have confirmed the feasibility and safety of organ preservation for pMMR locally advanced rectal cancer. Therefore, the high clinical and pathological complete response rates achieved by neoadjuvant immunotherapy for dMMR/MSI-H rectal cancer offer promising prospects for non-surgical treatment.