In this work, we point out that the width and the nature of the magnetic phase transition, TC value, and as well as magnetocaloric effect in La0.7-xSmxCa0.3MnO3 compounds can be easily modified through Sm-doped into La-site. With an increasing Sm concentration, a systematic decrease in the magnetization, TC, and magnetic entropy change (ΔSm) are observed. The Arrott-plot proveds that the samples with x = 0 and 0.1 undergoing a first-order phase transition. Meanwhile, sample x = 0.2 undergoes a second-order phase transition, which exhibits a high value of the relative cooling power (81.5 J/kg at ΔH = 10 kOe). An analysis of the critical behavior based on the modified Arrott plots method has been done for sample x = 0.2. The results proved a coexistence of the long- and short-range interactions in La0.5Sm0.2Ca0.3MnO3 compound.