Tension tests with two distinctly different strain rates, 2.8 × 10⁻⁵ and 2.8 × 10⁰ s⁻¹, have been performed on the (Fe,Ni)₃V long-range ordered (LRO) alloys in aged and unaged condition between 20 and 750°C. Tensile results as a function of test temperature indicate that the LRO alloys have good high-temperature strength. The yield strength of the ordered alloys increases with increasing test temperature, rather than decreasing as in conventional alloys. Long-term aging at 600°C has little or no effect on the elevated temperature tensile properties, and tends to reduce the sensitivity of aged materials to strain rate. The deformation mechanisms are changing as a function of test temperature, while there is a minor change in fracture characteristics over test temperature range. Oxidation features show the iron-base LRO alloys have limited oxidation resistance above 600°C.