The sintering temperature is a key way to tune the structural and magnetic properties of M-type hexaferrites. Here the effect of BaFe9.95Al2Mg0.05O19 M-type hexagonal Ba-hexaferrites, was studied. X-ray diffraction analysis revealed the presence of Fe2O3 impurity phases in all samples. The results showed that as the sintering temperature increased, the saturation magnetization (Ms) and remanence ratio (Mr/Ms) initially increased, then decreased at higher temperatures. On the other hand, the coercivity (Hc) and magnetocrystalline anisotropy field (Ha) decreased first, then increased. The average grain size (D) consistently grew between 800–2800 nm with increase in pre-sintering temperature. The optimal magnetic properties of BaFe9.95Al2Mg0.05O19 were achieved at a pre-sintering temperature of 1280 °C, with Ms = 49.94 emu g−1, Hc = 4.99 kOe, Ha = 1.5 kOe, and mB = 9.4097 μB. The findings suggest that magnetic properties of M-type hexagonal strontium ferrite can be significantly enhanced by optimizing the pre-sintering temperature, which has implications for the development of high-performance self-biased circulators, Magnetic filters and other magnetic applications.