Geometries of Mg_xAl_yN (x,y=1-5) clusters are studied by using hybrid density functional theory (B3LYP) with 6-311+G^* basis sets. For lowest-energy structures of Mg_xAl_yN clusters, stabilities and electronic properties are investigated. It shows that planar structures are dominant structures of Mg_xAl_yN (x+y≤4) clusters. The lowest-lying Mg_xAl_yN clusters mostly derived from ground-state structures of Al_nN or Mg_x-1Al_y+1N clusters. Mg_xAl_yN clusters are stable with respect to fragmentation into atoms or smaller clusters. Compared with neighboring clusters, MgAl₃N and Mg₃Al₃N clusters own higher stability. For all Mg_xAl_yN clusters studied, we found co-existence of covalent, ionic, and metallic bonding characteristics. Furthermore, ionization potential and electron affinity exhibit weak oscillations as increasing cluster size. Ro general pattern is observed.