Instrumented indentation has emerged as a robust technique for measuring mechanical properties of TS coatings.   Simple analyses of loading and/or unloading response are available to extract stress-strain behavior and elastic modulus, respectively.  A common consideration in such measurements is that indentation depth h be much less than coating thickness t in order to avoid ‘substrate effects’ and to extract intrinsic coating properties.  However, the effectiveness of this practice varies depending on the elastic or inelastic mismatch between coating and substrate.  In addition, for very thin coatings, microstructural size effects often necessitate h comparable to t.  Finally, interaction between coating and substrate (e.g., adhesion) is a highly relevant property that is not easily measured.  Here we present a systematic computational analysis of coating-substrate indentation, with variation in elastic-inelastic properties, and interfacial characteristics.  Results reveal significant effects on extracted properties, and suggest the possibility of simple indentation-based methods to probe coating-substrate interfaces.