The present work gives an account of the thermochemical studies of crystalline tris (acetylacetonato) manganese (III) compound. The heat of combustion (Δ_cH) and thereby standard heat of formation (Δ_fH^°) of crystalline tris (acetylacetonato) manganese (III) [Mn(C₅H₇O₂)₃(c)] has been measured experimentally with the help of static oxygen bomb calorimeter at 298 K and the values so obtained for Δ_cH and the Δ_fH^° have been compared with those available in literature to judge the efficacy of the present process. The values for Δ_cH and Δ_fH^° in the solid phase have been experimentally found to be - 8047∙371 k J mol^-1 and - 1341∙46 ± 15 kJ mol^-1 respectively.