Elektron21 (E21) and its composites with additions of 0.25 wt.%, 0.5 wt.%, and 1 wt.% AlN/Al nanoparticles (NPs) were fabricated by a high shear dispersion technology. Their creep properties were investigated over a stress range between 80 MPa and 140 MPa at 240°C. The grain size exhibits an obvious increase with the addition of AlN/Al NPs compared with the monolithic E21 alloy. Increasing the content of AlN/Al NPs leads to a pronounced improvement of creep resistance. Microstructural analysis shows that, with the addition of 1% AlN/Al NPs in E21, the distribution of the intermetallics Mg₃RE becomes much more homogeneous and their size is reduced. Such Mg₃RE particles can prevent the dislocation slip more efficiently during creep. Besides these Mg₃RE particles, the additional formation of Al₂RE and Al₂Zr₃ phases, which results from the reactions of AlN/Al NPs and the alloying elements Zr and REs, could act as thermal stable particles to improve the creep resistance. Finally, the remained AlN NPs without reactions are beneficial for the improvement of the creep resistance to some extent due to Orowan strengthening.