The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La2Ti2O7. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La2Ti2O7 produced nanoscale intergrowths of n?=?5 layered phase, while donor substitution produced nanoscale intergrowths of n?=?3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as ?20%. Pure La2Ti2O7 has a thermal conductivity value of ?1.3?W/m K which dropped to a value of ?1.12?W/m K for Sr doped La2Ti2O7 and ?0.93?W/m K for Ta doped La2Ti2O7 at 573?K.