A number of solution treated Mg-0.52Nd-0.08Zn-xZr (x = 0, 0.01, 0.03, 0.07, 0.12, and 0.14), Mg-yNd-0.08Zn-0.12Zr (y = 0, 0.17, 0.34, and 0.52) and Mg-0.52Nd-zZn-0.12Zr (z = 0, 0.08, 0.19, and 0.38) (at.%) cast alloys were investigated in terms of grain boundary and solid solution strengthening in this study. The hardness and yield strength of these alloys are determined by the average grain size (Zr content) and the concentration of Nd and Zn elements. The hardness can be predicted as HV5 a parts per thousand 23 + 3.07 d (-0.5) (m(-0.5)) + 26.5 C (Nd) (at.%) + 10.5 C (Zn) (at.%), with the average error of about 1.3 %. When the interactions among different solution atoms were not considered, the yield strength can be expressed as sigma(0.2) (MPa) = 21 + 0.42 d (-0.5) (m(-0.5)) + (813(3/2) C (Nd) (at. %) + 964(3/2) C (Zn) (at. %))(2/3), with the average error of about 2.0 %. When the interactions among different solution atoms were considered, more exact yield strength prediction could be obtained with the average error of about 1.6 %.