The far‐infrared spectral response of antiferromagnetic UO2has been studied between 10 and 220 cm−1as a function of temperature, magnetic field, and uniaxial strain. In the ordered state, resonant absorption is observed at 17.5, 79.0, 99.0, 110.5, 184.0, and 216.0 cm−1. The resonances at 79.0 cm−1and 99.0 cm−1are shown to be nondegenerate antiferromagnetic modes. Absorption by zone‐boundary magnons within domain walls is believed responsible for the structure at 17.5 cm−1. The remaining modes appear to be anomalous phonon absorptions which appear in the ordered state by virtue of the strong magnon‐phonon interaction.