In order to investigate the influence of solute atoms and particles on Young’s modulus of magnesium, series of binary Mg–Gd and Mg–Nd alloys were prepared using hot extrusion. With increasing Gd content from 0 to 2.654 at.% Young’s modulus of Mg–Gd alloys increases linearly from 44.0 to 45.3 GPa. Regarding Mg–Nd alloys, Young’s modulus firstly decreases to 42.5 GPa until 0.184 at.% Nd, and then increases to 43.4 GPa at Mg–0.628 at.% Nd. The different influences of solutes Gd and Nd on Young’s modulus of Mg are attributed to their different solid solution behaviors in magnesium, which can lead to the alterations of crystal cell parameters and/or different amount of second phases. For Mg–Gd alloys the lattice parameters increase and the axial ratio (c/a) decreases with Gd content increasing. In contrast, for Mg–Nd alloys they almost keep unchanged due to small solubility of Nd in Mg when Nd content increases.