Our study sheds light on the role of secondary phases in optimizing the magnetic properties of LSMO, offering valuable insights into the relationship between impurity phases, Curie temperature (T C), and magnetic entropy change. To achieve this goal, the Mn, Ni, and Mo elements were individually incorporated into the LSMO matrix to the formation of secondary phases. The solid-state reaction method was employed to create composite materials of (0.8) La 0.67 Sr 0.33 MnO 3+(0.2) A (A= Mn, Ni, and Mo). XRD and SEM results confirmed the successful formation of impurity phases within the main LSMO phase. From temperature-dependent magnetization (M (T)) measurements, it was determined that the T C of the samples approach towards room temperature with the existence of impurity phases. Additionally, the relationship between electron bandwidth (W) and T C was examined. The lowest T C value was observed for the lowest value of W. Besides these, the effect of the formation of impurity phases on the maximum magnetic entropy change () value is examined, and it is seen that impurity phases cause a decrease in the values.