The fields of cancer immunology and immunotherapy have made dramatic progress in the past 20 years. Various approaches to cancer immunotherapies, including cancer vaccines using peptides, proteins, DNA, and dendritic cells, have been developed to activate antigen-specific immune cells and their efficacy has been clinically examined. Herein, we summarize previously performed clinical trials of various immunotherapies against colorectal cancer (CRC), including our own novel immunotherapeutic approach, the “personalized peptide vaccine”, in which human leukocyte antigen (HLA)-matched vaccine peptides are selected based on pre-existing host immunity before vaccination. In the near future, neoepitopes identified through massive DNA sequencing of the genetic alterations in tumor cells, combined with robust T cell epitope predictions in each patient might be targeted as a personalized immunotherapy for CRC.