We report the observation of anomalous polarization coupling effects occurring in injection‐locked transversely excited atmospheric (TEA) CO2lasers, deduced from studies of the injection detuning parameter under varying conditions of polarization and injection power. For the special case of injection with orthogonally polarized radiation we have determined the existence of an optimum operation point, exhibiting minimum sensitivity of single mode operation to the detuning parameter. Off‐resonance injection locking of untuned TEA cavities is also discussed.