The propagation of thermoelastic harmonic waves in bilaminated periodic waveguide is studied in the context of the generalized theory of thermoelasticity. A continuum mixture theory is developed for waves traveling in the direction parallel to the layering. As a result, the problem is transformed into a quasi‐one‐dimensional one. The resulting approximate expressions are found useful in obtaining a qualitative description of the response. The symmetric mode of an exact solution is used to check the validity of the mixture theory. Quasi‐elastic and quasi‐thermal modes are investigated for the cases when the thermal relaxation time is either included or neglected. ©1996 American Institute of Physics.