The key to solve increasingly severe electromagnetic (EM) pollution is to explore sustainable, easily prepared, and cost-effective EM wave absorption materials with exceptional absorption capability. Herein, instead of anchoring on carbon materials in single layer, MoS₂ flower-like microspheres were stacked on the surface of pomelo peels-derived porous carbon nanosheets (C) to fabricate MoS₂@C nanocomposites by a facile solvothermal process. EM wave absorption performances of MoS₂@C nanocomposites in X-band were systematically investigated, indicating the minimum reflection loss (RL_min) of −62.3 dB (thickness of 2.88 mm) and effective absorption bandwidth (EAB) almost covering the whole X-band (thickness of 2.63 mm) with the filler loading of only 20 wt.%. Superior EM wave absorption performances of MoS₂@C nanocomposites could be attributed to the excellent impedance matching characteristic and dielectric loss capacity (conduction loss and polarization loss). This study revealed that the as-prepared MoS₂@C nanocomposites would be a novel prospective candidate for the sustainable EM absorbents with superior EM wave absorption performances.