The phase equilibria of the Fe-Mo-Ta ternary system at 800 and 1000 °C have been experimentally investigated. The various phases in the alloys after annealing at 800 °C for 60 days and 1000 °C for 45 days were examined using scanning electron microscopy, energy-dispersive x-ray spectroscopy and x-ray diffraction. Two three-phase regions were confirmed at 800 °C and two three-phase fields at 1000 °C. No ternary phase was observed in any of the alloys. The experimental results indicated that the solubility of Mo in the Fe7Ta6 phase and that of Ta in the Fe7Mo6 are large. The solubility of Mo in Fe7Ta6 is 16.5 at.% at 800 °C and 19.2 at.% at 1000 °C. In contrast, the solubility of Ta in Fe7Mo6 is 29.3 at.% at 800 °C and 15.7 at.% at 1000 °C. In addition, Fe2Ta and Fe2Mo can combine as a continuous solid solution, denoted as Fe2(Mo, Ta), in the 800 °C isothermal section.