We use molecular dynamics simulations to investigate the material properties of cubic zinc blende Si 0.5 Ge 0.5 alloy nanowire (NW). We elucidate the effect of nanowire size, crystal orientations, and temperature on the material properties. We found that the reduction in the NW cross-sectional area results in lower ultimate tensile strength (UTS) and Young’s modulus. The 111 and 110 oriented NWs exhibit the highest fracture strength and fracture toughness, respectively. The increased temperature degrades the strength of the material and facilitates failure. The vacancy defects introduced via removal of either Si or Ge atoms exhibit similar behavior, and linear reduction of UTS and Young’s modulus are realized with an increased vacancy concentration. We observed intrinsic failure characteristics of the NW as insensitive to the temperature. Overall, the new understanding of material properties and failure characteristics of Si 0.5 Ge 0.5 NW elicited in this study will be a guide for designing Si–Ge-based nanodevices. Graphical abstract