&nbsp;&nbsp;Mg-Al-Ca based alloys consist of the &alpha;-Mg matrix and continuous eutectic compounds along grain boundaries. Higher coverage of grain boundaries with the eutectic compounds results in high creep resistance. Intragranular precipitation caused by the rare earth (RE) addition is expected to improve creep resistance of the alloy. However, the aging treatment to produce precipitates results in the decreased grain boundary coverage due to the fragmentation of the eutectic compounds. Creep properties of Mg-Al-Ca alloys with and without RE were investigated after several aging treatments to elucidate the optimum condition of the aging treatments. The Mg-Al-Ca-RE alloy was aged at 423, 473, 523 and 573 K for 24 h respectively, and then was subjected to creep tests at 473 K under 100 MPa. The creep strength of the Mg-Al-Ca-RE alloy was higher than that of Mg-Al-Ca alloy due to the precipitates within grains. On the other hand, the creep rate of the Mg-Al-Ca-RE alloy increases with increasing aging temperature due to the fragmentation and spheroidization of the eutectic compounds along grain boundaries. Further improvement of the creep resistance is expected by the distribution of fine precipitates, which is considered to be achieved by the addition of high RE content.<br>