In this work, we have examined the waveguiding properties of photonic quasicrystalheterostructures based on the envelope approximation method. For determining the guidedmodes and the envelope of the field distribution in photonic quasicrystal heterostructuresbased on this technique, only knowledge of the photonic quasicrystal band structure andheterostructure design are required. It has been shown that the error incurred byapproximation through the envelope equation is an overestimation of about a few percentin comparison to the finite difference time domain method. Finally, it is revealed thatguided modes exist even in the case of an average refractive index that is lower in the corethan in the cladding material.