The magnetocaloric effect of Gd₅Si₂Ge₂ alloys under heat treatment conditions are investigated in low magnetic fields. The magnetocaloric effect (MCE) is studied by measuring magnetic entropy change (𝛥 𝑆_M) and adiabatic temperature change (𝛥 𝑇_ad) in a magnetic field of 1.5 T using a vibrating sample magnetometer (VSM) and a home-made magnetocaloric effect measuring apparatus, respectively. The maximum 𝛥 𝑆_M of the alloys increases by 200% from 4.38 to 13.32 J kg^-1 K^-1, the maximum 𝛥 𝑇_ad increases by 105% from 1.9 to 3.9 K when compared to the as-cast due to the homogeneous composition distribution and microstructure, while the magnetic ordering temperature is slightly reduced. These results indicate that the annealed Gd₅Si₂Ge₂ compounds are promising as high-performance magnetic refrigerants working room temperature in relatively low magnetic fields.