A holmium boride HoB50 polycrystalline sample was synthesised by boron-thermal reduction from the elements at high temperature. The temperature dependencies of the heat capacity Ср(Т) and the unit cell parameters a(T), b(T), c(T) of holmium boride were determined experimentally in the temperature range 2–300 K. In terms of Cp(T) dependence, smooth anomalies were revealed at TС1 max ≈ 6.5 K and TС2 max ≈ 30 K; the first of these is caused by an antiferromagnetic transition and the second by the influence of the crystalline electric field (CEF). The high-temperature anomaly in the heat capacity of the boride is satisfactorily reproduced due to a simplified scheme for CEF-splitting of the ground state of the Ho3+ ions.The dependencies a(T), b(T), c(T) of holmium boride clearly show a pronounced anisotropy of thermal expansion. The anomalies in the temperature changes of the HoB50 unit cell volume at elevated temperatures are analysed within the CEF model described above.