Hydrogen storage properties and structural properties in ZrFe2-xNix (x = 0.2, 0.4, 0.6, 0.8) alloys, prepared by arc melting in argon atmosphere, have been investigated. Powder XRD study shows that the lattice constants and the unit cell volume of ZrFe2-xNix (x = 0.2, 0.4, 0.6, 0.8) alloys having C15 Laves phase cubic structure decreases with increasing Ni content due to the smaller atomic radius of Ni compared to Fe. Surface morphology and elemental composition of the alloys were investigated by SEM and EDX. Hydrogen absorption pressure-composition (P-C) isotherms were investigated in the ranges 303 K <= T <=, 373 K and 0.5 bar <= P <= 50 bar using a Sievert type apparatus. The P-C isotherms show the single plateau region in the temperature and pressure range studied. The plateau pressure increases with increasing Ni content for a given temperature. The entropy and enthalpy of dissolved hydrogen in ZrFe2-xNix-H (x = 0.2, 0.4, 0.6, 0.8) have been calculated by means of the vant Hoff plot and the variation of these parameters with hydrogen content is discussed with respect to the existence of alpha, alpha + beta, and beta phase regions in the P-C isotherms. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.