Structural, magnetic, and magnetocaloric properties of the Mn1.2Fe0.8P1-xSixB0.03(x = 0.4, 0.5 and 0.55) phases have been investigated. The experimental results show that the critical behavior of the paramagnetic to ferromagnetic phase transition can be tuned through the P/Si ratio. An increase in the Si concentration not only raises the Curie temperature from 176 K to 280 K, but also changes the nature of the magnetic transition from the first order (for x = 0.4) to the second order (for x = 0.55) and, thereby, affects the magnetocaloric properties. The peak values of the thermal hysteresis and magnetic entropy change for a magnetic field change of 0-2T are 10 K, 4K, 0.8'K and 163, 8.7, 5.6 J kg(-1) K-1 for x = 0.4, 0.5, and 0.55, respectively. Mechanisms for the magnetic hysteresis loss and possibilities for the room temperature magnetic refrigeration are discussed. (C) 2016 Elsevier Ltd. All rights reserved.