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This study investigates the magnetocaloric effect in Nd₂Ni_1-xMo_xMnO₆ (x = 0, 0.05, 0.1) double perovskites, synthesized via the sol-gel method, exploring its potential as a green energy technology. The structural, magnetic, magnetocaloric, and critical exponents of the samples were investigated through experimental and theoretical approaches. X-ray analysis confirms that the compounds crystallize in a monoclinic structure with a P2₁/n space group, without detectable impurities. Mo doping leads to the formation of mixed-valence states of Ni, Mo, and Mn ions, as revealed by X-ray photoemission spectroscopy. The paramagnetic to ferromagnetic phase transition is observed at 196, 198, and 193 K for x = 0, 0.05, and 0.1, respectively, attributed to the Ni²⁺-O-Mn⁴⁺ superexchange interaction. Under an applied magnetic field of 2.5 T, the maximum magnetic entropy change (-ΔS_M) near the Curie temperature (T_C) is 1.51, 1.44, and 1.28 J kg^-1K^-1 for x = 0, 0.05, and 0.1, respectively. The corresponding relative cooling power (RCP) is 67, 61.5 and 57.2 J kg^-1 at 2.5 T for x = 0, 0.05, and 0.1, respectively Furthermore, the critical exponents are determined using an iterative method based on the Kouvel-Fisher analysis.