Mo-9Si-8B-3Hf alloy consisting of a Mo solid solution and intermetallic phases Mo3Si and Mo5SiB2 was fabricated by hot pressing sintering to yield a fine microstructure with all three phases being in the size range of micrometer. The tensile properties of this alloy at elevated temperature were evaluated in vacuum at elevated temperatures. This alloy displayed extensive plasticity or superplasticity at temperatures ranging from 1400 °C to 1560 °C with strain rate of 3×10-4 s-1. The tensile elongation of 410% is measured at 1560 °C. Grain boundary sliding is the main mechanism of plastic deformation for this alloy.