Two kinds of solidification paths from Y₃Al₅O₁₂ melt has been reported; one is stable Y₃Al₅O₁₂ (YAG) garnet, the other is metastable YAlO₃ perovskite (YAP) and subsequent YAP+Al₂O₃ eutectic. The reason for this, however, has been puzzled. The effect of cooling rate on this phase selection was addressed under containerless condition using an aero-acoustic levitator. A high-speed video camera (HSV) enabled us to directly observe the recalescence behavior. As the cooling rate increased from 15 to 350 K/s, the solidification of a metastable YAP and YAP+Al₂O₃ eutectic, a monophasic YAG, and an amorphous phase were successively obtained. At around the critical cooling rate of approximately 50 K/s for the formation of YAP and YAG, simultaneous recalescence of YAP and YAG was observed by HSV, and the sample obtained contained both the metastable YAP and stable YAG. The nucleation rate of YAG corresponds with that of YAP at the critical cooling rate and the growth velocity of YAP, which first nucleated in the undercooled melt, was slow enough for YAG to nucleate in the remaining undercooled melt, resulting the simultaneous recalescence. In general, the metastable phase nucleates at the higher cooling rate than the stable phase. However, in this system, the higher nucleation barrier of YAG than that of YAP led to the nucleation of YAG at the higher cooling rate.