As-cast Mg5Nd, Mg5Nd3Zn, Mg5Nd5Zn and Mg5Nd7Zn alloys were investigated with in situ synchrotron radiation diffraction during compression at 350°C. The results and the post-mortem microscopy investigations suggest that twinning was active during deformation, and was most pronounced in the binary alloy whereas in the ternary alloys grain rotation could be observed. Sub-grain formation could be detected in all the alloys. The reinforcing capacity of the intermetallic network was the largest in Mg5Nd and Mg5Nd3Zn.