The electrical and mechanical properties of atmospheric plasma sprayed (APS) yttria stablised zirconia (YSZ) thermal barrier coatings (TBCs) were determined using impedance spectroscopy and an indentation technique, respectively. Upon thermal exposure, sintering and phase transformation occurs in the YSZ TBCs, leading to changes in both the mechanical and electrical properties of the TBCs. After the thermal treatment, the formation of the monoclinic phase in the YSZ TBCs reduced the density of the TBCs and thus affected both the mechanical properties and conductivity of the TBCs. In this study, a relationship between the electrical and mechanical properties of APS TBCs has been established, allowing us to evaluate the properties of TBCs non-destructively with the use of impedance spectroscopy. © 2010 Elsevier B.V.