This communication describes the synthesis of Pt-M (M = Au, Ni, Pd) icosahedral nanocrystals based on the gas reducing agent in liquid solution method. Both CO gas and organic surface capping agents play critical roles in stabilizing the icosahedral shape with {111} surfaces. Among the Pt-M alloy icosahedral nanocrystals generated, Pt3Ni had an impressive ORR specific activity of 1.83 mA/cm(Pt)(2) and 0.62 A/mg(Pt). Our results further show that the area-specific activity, of icosahedral Pt3Ni catalysts was about 50% higher than that of the octahedral Pt,Ni catalysts (1.26 mA/cm(Pt)(2)), even though both shapes are bound by {111} facets. Density functional theory calculations and molecular dynamics simulations indicate that this improvement may arise from strain-induced electronic effects.