Reliable and realistic thermal properties data for investment casting shell molds are required to correctly simulate the solidification and predict the shrinkage. Investment casting shells exhibit several phase transformations during firing and pouring which affect their transient thermal properties. Due to phase transformation kinetics, these properties are dependent upon time, temperature and process history. This study presents the thermal properties (thermal conductivity and specific heat capacity) of seven industrially produced ceramic molds using an inverse method in which pure Ni was poured into ceramic molds equipped with two thermocouples (inside the mold cavity and in the shell). A new procedure for laser flash thermal property measurement was used as an initial point for the inverse method optimization. MAGMASOFT® software was used to simulate virtual cooling curves which were fitted to experimental curves by adjusting the temperature dependent thermal properties of the ceramic mold. The thermal properties data obtained from the inverse method were compared with measurement results from laser flash and the differences were discussed. The significance of the differences in property data is assessed by comparing simulation results between widely differing property data sets.