The effects of partial replacements of Zr by Y in the alloy Ni60Zr25-xAl8Yx (x=0 and 7 at %) on the crystallization behaviours of amorphous alloys were studied using isothermally heat-treated ribbons. With the partial replacement, the supercooled liquid region upon continuous heating was significantly extended indicating that crystallization can be effectively suppressed by the optimum amount of Zr replacement by Y. The first phase appeared during crystallization was identified as the ternary compound AlNi2Zr while the single exothermic event could be observed upon heating the amorphous ribbons. The AINi(2)Zr phase was decomposed into binary compounds upon further heating. Therefore, the extended supercooled liquid region of the alloy Ni60Zr25Al8Y7 was attributed to the suppression of AINi(2)Zr phase formation by the partial replacement of Zr by Y. The effects of Y on the crystallization behaviours were discussed on the basis of atomic configuration of the supercooled liquid.