This paper studies the effects of the Mn-site substitution by nickel on the magnetic properties and the magnetocaloric properties of La_0.7Ca_0.3Mn_1-xNi_xO₃ (x = 0, 0.05 and 0.1). The orthorhombic crystal structures of the samples are confirmed by the room temperature X-ray diffraction. The dependence of the Curie temperature (T_C) and the magnetic entropy change (ΔS_M) on the Ni doping content was investigated. The samples with x = 0 had the first order phase transition, while the samples with x = 0.05 and 0.1 had the second order phase transition. As the concentration of Ni increased, the maximum entropy change (|ΔS_M|_max) decreased gradually, from 2.78 J·kg⁻¹·K⁻¹ (x = 0) to 1.02 J·kg⁻¹·K⁻¹ (x = 0.1), in a magnetic field change of 15 kOe. The measured value of TC was 185 K, 150 K and 145 K for x = 0, 0.05 and 0.1, respectively. The phase transition temperatures became wider as x increased. It indicates that the Mn-site substitution by Ni may be used to tailor the Curie temperature in La_0.7Ca_0.3Mn_1-xNi_xO_3.