Structural, magnetic, and magnetocaloric properties of La_0.6Sr_0.2Ba_0.2-x◻_xMnO₃ (0 ≤ x ≤ 0.15) where ◻ is a barium deficiency have been investigated by X-ray diffraction and magnetic measurements. Our samples were synthesized using the solid-state reaction method at high temperatures. Structural studies show that our samples are single phase and crystallize in the rhombohedral system with $R\hspace{0.17em}\overline{3}\hspace{0.17em}c$ space group. Magnetization measurements as a function of temperature in a magnetic applied field of 0.05 T show that all our samples exhibit a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T_C shifts to lower values with increasing barium-deficiency. The Arrott plots show that the phase transition is of second order. The effect of barium deficiency on the magnetocaloric properties has been investigated. The values of the maximum of the magnetic entropy change, $\left|-\Delta S^{\max }\right|$ , under a magnetic field change of 3.5 T are found to be 2.9, 2.92, 3.31, and 3.34 J/kg K for x = 0.0, 0.05, 0.1, and 0.15, respectively.