The structural, magnetic and magnetocaloric properties of Gd55Co20Fe5Al20-xSix (x=0, 2, 5, 10, 15, 20) alloys have been investigated in detail for the first time. The broad diffraction peaks for x=0 and 2 indicated that the samples have amorphous structures. For higher Si content (x >= 5), some diffraction peaks revealed that the Si substitution increases the crystallinity of the alloys. While the magnetization curves showed only one magnetic transition for low Si content, for the higher concentrations a second magnetic transition was observed due to the crystallization of the samples. The maximum entropy change of 8.01 J/kg K was observed in a 5 T magnetic field for the x=0 sample and decreased with further increase of Si concentration. The refrigerant capacities vary from 913 J/kg for x=0 to 596 J/kg for x=15. (C) 2013 Elsevier B.V. All rights reserved.