The grain growth behavior of a Zr2Cu crystalline phase from a supercooled liquid region of Zr65Cu27.5Al7.5 and Zr65Cu35 metallic glasses was examined as a function of annealing time, t(a) at various temperatures. Since no distinct change of constitution and strain in Zr2Cu phase is seen, the grain size calculated from a line-broadening of X-ray diffraction peak by Scherrer's formula can be used. The calculated grain size is in agreement with that obtained by transmission electron microscopy observation. The curve of grain size with t(a) is parabolic. The grain growth in Zr65Cu35 takes place at lower temperature and its rate is extremely larger as compared with those of Zr65Cu27.5Al7.5. These differences are originated from the suppression of growth of Zr2Cu by Al atom, which retards the diffusion of Cu owing to the primary precipitation of ZrAl in Zr65Cu27.5Al7.5. The formation of ZrAl may be attributed to the strong chemical affinity between Al and Zr. The activation energies for grain growth of 115 kJ mol(-1) for Zr65Cu27.5Al7.5 and 363 kJ mol(-1) for Zr65Cu35 are obtained by the Arrhenius plot of grain growth rate against a reciprocal of temperature. These activation energies reflect the kind and/or magnitude of diffusion atoms during the grain growth.