The corrosion behavior of rapidly solidified (RS) Mg-Zn-Y alloy ribbons have been investigated using hydrogen evolution testing in 1 wt% NaCl solution open to air at 298 K. The corrosion rates of Mg(100-x-y)ZnxYy (x = 0.90-2.14, y = 1.58-1.92, at%) RS alloys were sensitively influenced by their alloy compositions. Zinc content has no effect on improvement of corrosion resistance, while the corrosion resistance was improved by adding 1.92 at% of yttrium. The Mg97.16Zn0.92Y1.92 RS alloy exhibits the highest corrosion-resistance in this study. The effect of heat treatment on the corrosion behavior has also been studied for the Mg97.16Zn0.92Y1.92 RS alloy. The dissolution rate of the heat-treated RS alloy is higher than that of the untreated alloy. The deterioration of corrosion resistance by the heat treatment was due to the precipitation of Mg24Y5 phase.