Molybdenum disilicide (MoSi 2 ) sheath and aluminum oxide (Al 2 O 3 ) core blended powders were fabricated by spray drying. A derived coating material was produced for the application as microwave absorbers using the as prepared powders by atmospheric plasma spray (APS) technology. The effects of MoSi 2 /Al 2 O 3 mass ratio on the dielectric and physical mechanical properties of the composite coatings were investigated. When the MoSi 2 content of the composites increases from 0 to 45%, the flexure strength and fracture toughness improve from 198 to 324 MPa and 3.05 to 4.82 MPa·m 1/2 then decline to 310 MPa and 4.67 MPa·m 1/2 , respectively. The dielectric loss tangent increases with increasing MoSi 2 content, and the real part of permittivity decreases conversely over the frequency range of 8.2–12.4 GHz. These effects are due to the agglomeration of early molten MoSi 2 particles and the increase of the electrical conductivity with increasing MoSi 2 content.