Polyaniline polymer-coated MnTi-substituted strontium hexaferrite (Sr(MnTi) (x) Fe12-2x O-19/PANI, x = 1.0, 1.5, 2.0) composites were synthesized by the oxidative chemical polymerization of aniline in the presence of ammonium peroxydisulfate. The structure and morphologies of the products were characterized by X-ray diffraction, FT-IR, TGA, SEM, and TEM. In the magnetization for the Sr(MnTi) (x) Fe12-2x O-19/PANI composites, it was found that the saturation magnetization (M (s)) and coercivity (H (c)) decreased after polyaniline coating. The composite under an applied magnetic field exhibited hysteretic loops of ferromagnetic behavior, such as high saturation magnetization (M (s) = 12.1-1.9 emu/g) and coercivity (H (c) = 0.919-0.084 kG). The composite specimens of core-shell Sr(MnTi) (x) Fe12-2x O-19/PANI and thermal plastic resin had a band-width microwave absorption due to the reflection losses from -15 to -35 dB at frequencies between 18 and 40 GHz as observed by a high-frequency network analyzer.