Copper (Cu) was cryogenically milled with tungsten (W) in a high-energy ball mill. The process created W particles dispersed in a nanocrystalline Cu matrix. These “alloys” were then annealed to a maximum temperature of 800°C. The addition of W stabilized the Cu at∼40nm during annealing to 400°C for a 1at% W composition and to 600°C for 10at% W. As evidenced through hardness measurement, the W provided a significant increase in strength over pure Cu, and the 10at% W material maintained a 2.6GPa hardness after annealing at 800°C. The stabilization and strengthening mechanisms are compared against theoretical prediction and found to be in good agreement. Although the strength and stability are significantly improved over pure Cu, the maximum benefit was hindered by an extremely broad W particle size distribution (∼5–5000nm). For the 10at% W alloy, only half of the added W was reduced to nanoscale where kinetic pinning and strengthening become most effective.