The structures of MgNi nanoparticles are searched for by a computational methodology combining atomistic model-ing, global optimization searches and density-functional the-ory (DFT) calculations. Sizes up to 45 atoms are consid-ered for several different compositions. Core-shell structures are found in most cases. However, there are also excep-tions, such as the three-shell high-symmetry matryoshka clus-ters Mg@Ni 12 @Mg 32 (of anti-Mackay icosahedral geometry) Mg@Ni 12 @Mg 14 (of tetrahexadral geometry). Other high-symmetry structures comprise the core-shell cubic Mg 8 Ni 6 , the tetrahexahedral cluster Mg 14 Ni 13 and the pentadocahedral cluster Mg 21 Ni 12 . The results of the atomistic models is com-pared with DFT calculations obtaining a good agreement.