In electro-Fenton process, carbon-based materials, particularly 3D carbon felt, are the best choices for the cathodic electrodes because of several advantages such as low cost, excellent electrolytic efficiency, high surface area, and porosity. In this chapter, various aspects of this material are discussed in detail. This chapter is divided into three main sections, including (1) characterization of carbon felt (CF), (2) modification of CF, and (3) application of CF in electro-Fenton (EF) process to remove biorefractory pollutants. First of all, the typical characteristics of CF such as morphology, porosity, and conductivity are discussed. Next, in the modification section, we introduce different methods to improve the performance of CF. We especially focus on the surface area and electrochemical activity toward electrodes applications. Finally, both modified and non-modified CF is used as cathode materials for EF systems like homogeneous, heterogeneous, hybrid, or pilot-scale types.