The Mn1.15Fe0.85P0.52Si0.45B0.03 rods were prepared by copper mould suction casting. The effects of heat treatments on the structure and magnetocaloric properties have been investigated. The X-ray diffraction patterns indicated that the annealed Mn1.15Fe0.85P0.52Si0.45B0.03 rods present hexagonal Fe2P-type structure with a small amount of Mn3Fe2Si3 impurity. With elevated annealing temperatures from 1123 K to 1423 K, the Curie temperature increases from 205 K to 251 K, the magnetic entropy change jumps from 0.6 to 19.8 J kg–1K−1 under a magnetic field change of 0–2 T and the thermal hysteresis is reduced from 17 K to 10.5 K. Thus, the heat treatment is suggested to be an effective way to enhance the magnetocaloric effects of Mn1.15Fe0.85P0.52Si0.45B0.03 alloys.