A study has been made of spin waves in the antiferro‐, ferri‐, and ferromagnetic phases of FeCl2·2H2O. These levels are found to interact strongly with a field independent level at 31.5 cm−1. A similar interaction is found in CoCl2·2H2O near 29.3 cm−1. This field independent level has been tentatively identified as ak=0, low‐lying optical phonon. This phonon appears to be infrared active only because of its coupling with nearby magnon levels. The experimental data for both materials is well described by a phenomenological magnon‐phonon interaction.