The materials used to restore bone defets have a number of systemic limitations. The metal implants showing high mechanical strength have an insufficient osseointegration capability, while ceramic and polymer materials have better biocompatibility, but do not meet the requirements of mechanical reliability in the zones of considerable load. In this regard, the study of new classes of materials combining the strength characteristics with the osseogenic potential seems to be a promising area. The study aimed to assess cytocompatibility of the boron carbide (B₄C)-based porous ceramic material to confirm the possibility of its use for bone defect replacement. The B₄C semi-finished products were manufactured by pressureless sintering at 1900–2100 °C; ultrastructure of the resulting sample surface was examined by atomic force and scanning electron microscopy. Citotoxicity of the B₄C samples was estimated by an indirect method relative to human mesenchymal stem cells. The following cell survival rates were reported: 102.1% (24 h) and 99.1% (72 h) for the samples autoclaved; 110.0% (24 h) and 94.4% (72 h) for those treated with ethylene oxide. No significant intergroup differences were revealed (Mann–Whitney U-test). The findings allow us to consider B₄C ceramics as a promising solution for bone grafting. However, further research is required to assess its clinical potential, including the development of sterilization protocols for larger and complex-shaped samples.