Nanomedicine is an arising field that exploits nanotechnology concepts for pioneered therapy and diagnostics. Colorimetric sensors for tumor markers have displayed interesting benefits compared to conventional systems in clinical laboratory diagnosis. Colorimetric immunoassay-based approaches show up-and-coming results since the goal cancer marker is determined with high sensitivity but without the utilization of advanced/- expensive techniques through an effortless optical color change. Also, colorimetric biosensor has the potential to detect proteins in biological fluids swiftly with high sensitivity, and they are anticipated to play a progressively serious role in tumor diagnosis. We reviewed (covering the period 2015-2020) various studies based on colorimetric sensing strategy using nanostructured materials (highly efficient enzyme mimics, artificial enzymes or nanozymes) to detect different tumor antigens in biological fluids. Specifically, we highlighted the recent progress and efforts in the construction of colorimetric immunosensors. Colorimetric immunosensors can be roughly divided into two main categories: transition metal nanozyme-based sensing and noble metal nanozyme-based sensing.