Spin-wave resonances in pelletized powder of bismuth orthoferrite (BiFeO3) were studied in transmission spectroscopy at frequencies of 0.1–0.75 THz and in the temperature range of 300–650 K. A vector network analyzer with frequency extenders was used in conjunction with temperature scans.We extended the experimental coverage of spin-wave resonances in BiFeO3 up to almost the Néel temperature. We observed that \psi^(1)_1 and \psi^(2)_1 modes are degenerate around 420 K due to the temperature dependences of the magnetic anisotropy and the Dzyaloshinskii-Moriya interaction.