In situ deformation experiments were performed in a transmission electron microscope to investigate the mechanical properties of submicron-sized Pd 40Cu30Ni10P20 metallic glass (MG) wires. Results show that the submicron-sized MG wires exhibit intrinsic ultrahigh tensile strength of 2.8 GPa, which is nearly twice as high as that in their bulk counterpart, and 5% elastic strain approaching the elastic limits. The tensile strength, engineering strain at failure and deformation mode of the submicron-sized MG wires depend on the diameter of the wires. 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.