OBJECTIVE: As the development and progression of colorectal cancer (CRC) are known to be affected by the immune system, cell subsets such as T cells, natural killer (NK) cells, and natural killer T (NKT) cells are considered interesting targets for immunotherapy and clinical biomarker research. Until now, the role of systemic immune profiles in tumor progression remains unclear. In this study, we aimed to characterize the immunophenotype of circulating T cells, NK cells, and NKT-like cells in patients with CRC, and to subsequently correlate these immunophenotypes to clinical follow-up data. METHODS: Using multiparameter flow cytometry, the subset distribution and immunophenotype of T cells (CD3CD56), CD56 NK cells (CD3CD56), CD56 NK cells (CD3CD56), and NKT-like (CD3CD56) cells were investigated in peripheral blood mononuclear cell (PBMC) samples from 71 CRC patients and 19 healthy donors. RESULTS: CRC patients showed profound differences in immune cell subset distribution and their immunophenotype compared to healthy donors, as characterized by increased percentage of regulatory T cells, and reduced expression level of the natural cytotoxicity receptors NKp44 and NKp46 on both CD56 NK cells and NKT-like cells. Finally, we showed in a multivariate analysis that above-median percentage of CD16 NKT-like cells was independently associated with shorter disease-free survival in CRC patients. CONCLUSION: The altered phenotype of circulating immune cell subsets in CRC and its association with clinical outcome highlight the potential use of PBMC subsets as prognostic biomarkers in CRC, thereby contributing to better insight into the role of systemic immune profiles in tumor progression.