In this study, standard 100 mm x 200 mm geopolymer and OPC concrete cylinder specimens were subjected to fires up to 1000 oC with the heating rate similar to that of ISO 834 standard. Both types of concrete cylinders were exposed to identical temperature profile and the transfer of heat inside the specimens was recorded by using thermocouples. The damages in terms of cracking and spalling of the specimens during fire exposure and after cooling down to room temperature were determined. The specimens were then weighed to determine the mass loss and subjected to compression tests to determine the residual strengths. Scanning electron microscopic images were obtained to observe the microstructure of the geopoly- mer matrix after exposure to high temperature fires.