ObjectiveTo understand the effect of programmed death-1 (PD-1) inhibitors on defective mismatch repair (dMMR) / microsatellite instability-high (MSI-H) advanced colorectal cancer (CRC). MethodThe literature of recent research relevant PD-1 inhibitors in the utility for patients with dMMR/MSI-H advanced CRC was reviewed and summarized. ResultsAt present, there were many studies exploring the utility of anti-PD-1 inhibitors for the treatment of dMMR/MSI-H advanced CRC (including locally advanced CRC and metastatic CRC), and some studies were still in trials. Studies had consistently shown that the use of PD-1 inhibitors in dMMR/MSI-H advanced CRC as first-line or subsequent therapy, as well as in the neoadjuvant setting, leading to significant survival benefits. These benefits were particularly notable in cases of dMMR/MSI-H metastatic CRC with concurrent BRAF/RAS mutations and in the context of neoadjuvant immunotherapy aimed at organ preservation in locally advanced dMMR/MSI-H CRC. Moreover, there were numerous studies exploring “dual immunotherapy”, and most studies found that its efficacy was superior to that of single immunotherapy. However, the more adverse events were reported by the “dual immunotherapy” compared to the single immunotherapy. ConclusionsOverall, based on results of the literature reviewed, PD-1 inhibitors have shown significant clinical benefits in dMMR/MSI-H advanced CRC, but there are still more issues that need to be further explored, such as discovering more first-line PD-1 inhibitors, overcoming drug resistance and adverse events. Future clinical practice should prioritize more precise individualized identification and the application of more effective combination therapy regimens to further optimize outcomes for patients with dMMR/MSI-H advanced CRC.