Achieving high-performance electromagnetic wave absorption (EMWA) capacity at thinner thicknesses remains a critical yet challenging objective. In this study, Dy₂O₃/Fe₃C/N-doped carbon (DFC) composites were synthesized via a solvothermal process followed by high-temperature carbonization, with metal-organic frameworks (MOFs) used as precursors. By systematically adjusting the molar ratio of Dy³⁺/Fe³⁺, the dielectric and magnetic properties of the materials were synergistically optimized. The EMWA performance exhibited a nonmonotonic dependence on the Dy³⁺ content, first increasing before decreasing at higher concentrations. At an optimal Dy³⁺/Fe³⁺ molar ratio of 1.2 : 0.8, the DFC composites demonstrated a remarkable minimum reflection loss value of −56.08 dB at a mere 1.76 mm thickness, alongside an effective absorption bandwidth value of 5.12 GHz (12.56–17.68 GHz). The exceptional EMWA performance stems from optimized impedance matching, multiple scattering and reflections, dielectric loss, and magnetic loss. Furthermore, radar cross-section simulations validated the material’s practical applicability. Therefore, this work provides a novel strategy for designing next-generation EMWA materials with ultra-thin profiles and wideband absorption capabilities.