Abstract: In recent years, electromagnetic wave (EMW) absorption has been extensively investigated for solving EMW radiation and pollution. The metal–organic frameworks (MOFs) have attracted attention due to their low density and unique structure, which can meet the requirements of strong reflection loss (RL) and wide absorption bandwidth of EMW absorption materials. In this manuscript, indium nanoparticles/porous carbon (In/C) nanorods composites were prepared via the pyrolysis of nanorods-like In-MOFs at a low temperature of 450°C. Indium nanoparticles are evenly attached and embedded on porous carbon. Low electrical conductivity of In/C nanorods is unfavorable to EMW absorption performance, which is due to the low temperature carbonization. Thus, graphene (Gr) nanosheets with high electrical conductivity are introduced to adjust electromagnetic parameters of In/C nanorods for enhancing EMW absorption. The minimum RL of the In/C-Gr-4 composite is up to −43.7 dB with a thin thickness of 1.30 mm. In addition, when the thickness is further reduced to 1.14 mm, the minimum RL of −39.3 dB at 16.1 GHz and effective absorption bandwidth of 3.7 GHz (from 14.3 to 18.0 GHz) can be achieved. This work indicates that In/C-Gr composites show excellent EMW absorption performance.