Fe-Fe3C@C composites are successfully synthesized via a facile pyrolysis process. Experimental results indicate that Fe-Fe3C nanoparticles are closely parceled among amorphous carbon and exhibit a core–shell structure. The obtained materials display excellent microwave absorption performance with an optimal reflection loss of − 35.6 dB at 17.2 GHz, and an effective absorbing bandwidth of 4 GHz (from 12.4 to 16.4 GHz) with the coating thickness of 2 mm. The magnetic loss derived from Fe core and dielectric loss on carbon materials as well as a good impedance matching are believed to play decisive roles for this favorable microwave absorbing properties. The composites are considered to be good candidates for microwave absorption applications.