The dependences of the thermoelectric properties of (001)KCl/PbTe/SnTe/PbTe three-layer structures on the SnTe layer thickness (d
SnTe = 0.5–6.0 nm) at a fixed thickness of PbTe layers were studied. It was established that the thickness dependences of the Seebeck coefficient, the Hall coefficient, electrical conductivity, charge carrier mobility, and the thermoelectric power factor are distinctly non-monotonic. Two possible reasons for this non-monotonic behavior of the thickness dependences of the thermoelectric properties are considered: the size quantization of the energy spectrum in a SnTe quantum well and / or the formation of edge misfit dislocations at the interfaces after reaching the critical thickness, which corresponds to the transition from a pseudomorphic growth to the introduction of misfit dislocations at the interfaces. It is suggested that the observed effect has a general character and should be taken into account when optimizing thermoelectric properties of superlattices.