Thermal shock behaviour of alumina-mullite-zircon refractories was investigated by varying zircon content. Thermal shock parameters R and R-st based on the room temperature mechanical measurements were calculated as a function of zircon content in order to foresee thermal shock behaviour of refractory materials. The R parameter, predicting the resistance of a material to the initial shock and expressed as the difficulty of crack initiation, showed an similar to1.5 times increase with the addition of zircon. Furthermore, R-st parameter also supported that there was a significant improvement (by a factor of >2) in the maximum allowable temperature difference required to propagate long cracks under severe thermal stress conditions. Thermal shock testing was then carried out based on the bend strength and Young's modulus values as a function of quench temperature. The predictions made from R and R-st parameters were matched by thermal shock testing data. The refractory containing 20% zircon showed the highest resistance to both crack initiation and propagation, leading to a high resistance to fracture for a long-life performance in service for high temperature applications.