Co substitution in hexaferrites Sr1−xCoxFe12O19 compounds with doping values x = 0.0, 0.075, 0.15, 0.225 and 0.30 were prepared using microwave digestion system. Structural, morphological, magnetic and dialectic properties were investigated. X-ray diffraction pattern proved a hexagonal phase (SrFe12O19) existing as a main phase for all samples. The lattice parameters, crystallites size and other parameters such as microstrain and direct cell volume and dislocation density were calculated from the Rietveld refinement of the X-ray results. The SEM and TEM results confirmed a hexagonal structure existing. The histogram of the particle size distribution showed variation of the grain size with nano range between 90 nm and 178 nm. Magnetic results showed that the magnetization (M), saturation magnetization (Ms), and remnant magnetization (Mr) increased with increasing of Co substitution while the coercive magnetic field, Hc, fluctuated with increase of Co substitution because of the irregular change of the grain size of the samples. The sample x = 0.15 has a low coercive field because of the uniformity of the crystal grains. Such magnetic properties recommend this sample to be used in magnetic applications. The dielectric study of these samples revealed that the AC conductivity, σ, increases with increasing the frequency while impedance (Z), dielectric constant (ε), dielectric loss, and tan δ decrease exponentially with F(Hz). The dissipation factor was found to have a convert frequency point at low F(Hz) after its starting to decrease slowly to the end of F-range. These dielectric properties suggest the validity of these hexaferrites compounds to be used as a capacitor.