[en] We have studied the influence of Pt-Ni substitution on the crystal structure and magnetic behavior of the PrNi_1-x Pt _x pseudobinary compounds. The orthorhombic CrB-type structure owned by PrNi was found to remain conserved when substituting Pt for Ni while the unit cell volume linearly increased. The polycrystalline PrNi_1-x Pt _x samples were investigated by measuring the specific heat (C_P ) and magnetization (M) as function of temperature and magnetic field. All studied compounds were found to order ferromagnetically; the Curie temperature T _C is linearly decreasing with increasing Pt content. The magnetocaloric effect (the isothermal magnetic entropy change ΔS _mag) was determined consistently from the specific heat and magnetization data. The maximum values of ΔS _mag are the same for the boundary compounds PrNi and PrPt but become somewhat reduced in solid solutions