Treatment of locally advanced rectal cancer involves neoadjuvant chemoradiotherapy (CRT), including induction or consolidation chemotherapy. Introduction of immunotherapy has brought success in several solid tumors and hematological diseases. In colorectal tumors, it was only introduced later. A general predictive biomarker is the deficient mismach repair (dMMR) status and consequent microsatellite instability (MSI-H). In these tumors, immune checkpoint inhibitor (ICI) therapy is the first-choice therapy in metastatic colorectal cancer. ICIs have been used in earlier, non-metastatic stages in several studies, with breakthrough results in the microsatellite-unstable patient group and recently in combination with neoadjuvant CRT in rectal tumor patients with pMMR/MSI-L status. In our report we focused on the recent immune checkpoint inhibitor treatment of metastatic and locally advanced colorectal cancer, as a monotherapy, or combined with chemo- or radiotherapy. We summarize the studies with the most promising results.