This paper describes the characteristics of akermanite-gehlenite and diopside bioceramics derived from the CaO-MgO-Al₂O₃-SiO₂ system as a potential bone substitute material. The akermanite-gehlenite and diopside bioceramics were synthesised for 4 h at 500 rpm via the wet mechanochemical process. The resultant powder was sintered at 1050 and 1150 °C for 1 h to obtain the akermanite-gehlenite and diopside bioceramics. The bioceramic’s microstructural, physical, and mechanical properties were investigated comparatively. XRD diffraction, FTIR and scanning electron microscopy, with energy dispersive spectroscopy (SEM-EDS) analysis, were conducted to characterise the samples. The bioceramic samples’ linear shrinkage, density, porosity, and water contact angle were analysed to determine their physical properties. The mechanical properties of the samples were determined using compressive tests before and after undergoing in vitro bioactivity. The in vitro bioactivity of the bioceramic was investigated by analysing its apatite-forming ability in a simulated body fluid (SBF) at 37 °C. XRD patterns, SEM micrographs, and FTIR spectra for pellets sintered at 1050 °C indicated the presence of apatite particles on their surfaces. The pellets’ compressive strength before being immersed in SBF ranged between 24.42 ± 1.5 and 24.93 ± 1.7 MPa. The compressive strength of the pellets noticeably decreased to 34.4% and 40.7% after 14 days of immersion in SBF. In conclusion, the akermanite-gehlenite bioceramic prepared using the wet mechanochemical method can potentially become a bone substitute.