Ir1–xRex (0.15 ≤ x ≤ 0.40) phases prepared under high-pressure, high-temperature conditions from nanopowders of iridium and rhenium were characterized using powder X-ray diffraction and scanning electron microscopy. Structural characteristics of the phases obtained were identical with the corresponding parameters for the solid solutions prepared by means of melting and thermal decomposition of the precursors. The data obtained make it possible to improve solid-state solubility limits in the binary Ir–Re phase diagram. As revealed, the maximum solid solubility of Ir in Re is 68 at.%, and that of Re in Ir is 20 at.%.