An ultrahigh-purity Ti-45 mol%Al alloy ingot was isothermally hot-pressed along each of the X, Y and Z coordinates at 1473 K. The hot-pressed ingot consisted mainly of very fine recrystallized grains, with an average size of 5 µm. The mechanical properties of this finegrained Ti-Al alloy were examined by tensile test at 293 K, 823 K, and 923 K at strain rate of 1.1 × 10 −4 s −1 in a vacuum of 1.3 × 10 −3 Pa. The ductile-brittle transition temperature (DBTT) was determined by the tensile tests and scanning electron microscope observation of the fracture surfaces of the samples. This ultrahigh-purity Ti-45 mol%Al alloy showed the following excellent high-temperature mechanical properties: (1) The 0.2% proof strength was 486 MPa and elongation at 923 K was 45%. (2) The DBTT was 870 K, which is about 200 K lower than that of conventional binary Ti-Al alloys with similar composition.