The paper presents the results of studying the Mossbauer effect on alloys of the multicomponent system (Tb1-XYX)0.8Sm0.2Fe2 (substitution parameter X = 0, 0.2, 0.4, 0.6, 0.8, 1). This system is based on the TbFe2 compound, which has a cubic crystal structure and the highest magnetostriction constants among rare-earth intermetallic compounds of the RFe2 type. Substitution of atoms magnetic terbium for weakly magnetic samarium (20%) and nonmagnetic yttrium leads to exchange interactions altering in the system which should affect the magnitude of hyperfine interactions on 57Fe nuclei in alloys of this system. The studies were carried out at room temperature. All parameters of the Mossbauer spectrum being isotropic and anisotropic hyperfine fields, quadrupole shift of the components of the spectrum hyperfine structure, and isomeric shift of the Mossbauer line have been determined. Their dependences on the concentration of yttrium have been established.