Carbon materials are widely used industrially as an adsorbent for purification to remove pollutants. Carbon materials are known to have excellent adsorption efficiency for ionic pollutants. This is because its adsorption capacity is high due to the porous structure and large specific surface area. In particular, activated carbons, one of porous carbon materials, can be used repeatedly with easy recycling and has excellent economic efficiency. Furthermore, improving the adsorption performance through treating the surface of activated carbons is being actively researched. Among the various pollutants, radioactive metal ions are the most harmful pollutants to living organisms due to its high gamma-ray emission, water solubility, mobility, and long half-life. This article covers the surface modifications of carbon based adsorbents and their application for radionuclide removal. Oxygen functional groups are introduced to enhance the ion adsorption performance by increasing the electrostatic interaction. Carbon materials hybridized with metal hexacyanoferrates have been attracting attention as they selectively remove cesium. In this review, effective surface treatment methods are introduced that utilize activated carbon for the removal of ionic radionuclides.