Indentation microhardness testing was used to assess the microhardness of an EB-PVD thermal barrier coatings (TBCs) deposited on a single crystal Ni-base superalloy substrate. Tests performed using a Knoop indenter geometry reveal that there is an indentation size effect (ISE), namely that the apparent microhardness decrease significantly with increasing indentation test load. An energy balance analysis based on elastic/plastic indentation model was applied to analyze the apparent ISE and to extract the load-independent hardness from the experimental measurements.