High-entropy alloys (HEAs) have become newly emerging candidates as structural materials of advanced fission reactor because of their excellent mechanical properties and irradiation resistance. Recently, carbon doped HEAs exhibited improved mechanical properties, such as yield strength and elongation. However, the effects of carbon doping on the irradiation resistance of HEAs need further investigation. Here, the irradiation-induced defects and irradiation hardening of Fe38Mn40Ni11Al4Cr7 HEA with different carbon contents were investigated by using 5 MeV Xe23+ heavy-ion irradiation at room temperature, and multiple characterization methods were used to provide the essential evidences. Results showed that the carbon doped samples exhibited smaller-sized dislocation loops and significantly lower hardening rate than those of undoped samples. The reason is attributed to two aspects: Firstly, interstitial carbon would significantly increase lattice distortion and migration energy of self-interstitial atoms, thereby inhibiting the formation of defects. Secondly, carbon atoms would act as obstacles that hindered the evolution of defects. Consequently, our study indicated the potential of using carbon doped HEAs as irradiation-resistant materials. (C) 2020 Elsevier B.V. All rights reserved.