High-performance microwave absorbing materials (MAMs) play a vital role in electromagnetic (EM) pollution protection. Multi-interfacial heterogeneous structure design has become a mainstream direction for designing and fabricating excellent MAMs. Herein, multi-interfacial hollow core-shelled yttrium aluminum garnet@nitrogen-doped carbon (YAG@NC) composites were synthesized by coprecipitation, thermal treatment, self-polymerization and carbonization processes. Thermal treatment temperatures were used to regulate the defect level and interfaces in carbon materials. Defects of NC and multiple interfaces favor dielectric polarization, and the hollow cavity endows the MAMs with lightweight characteristics and ideal impedance matching. The results indicated that YAG@NC composites possess excellent microwave absorption properties with an effective absorption bandwidth (EAB) of 5.5 GHz at an absorber thickness of only 1.95 mm. The radar cross section (RCS) reduction of YAG@NC composites was verified by CST simulation in the far field, and the strongest RCS reduction value was up to 32.64 dBm with a scattering angle of 0°. This work paves the way for designing multicomponent microstructure dielectric loss absorbers with broadband and strong microwave absorption.