Fire resistance of geopolymer concrete is superior to that of ordinary Portland cement (OPC)-based concrete. However, vulnerability of geopolymer concrete when exposed to real fire events is an issue. In view of the issue, a comparative evaluation of the fire resistances of OPC-based and geopolymer concrete was performed. OPC-based and fly-ash (FA)-based geopolymer concrete specimens were prepared with a standard strength grade of 60 MPa. A laboratory-scale simulation of real fire events was conducted by exposing the specimens to fire at 200, 500 and 1000 °C for 2 h. Fire resistances of the specimens were evaluated by performing tests to determine mass loss and residual compressive strength and thermogravimetric analyses (TGA) before and after exposure to fire. Due to water evaporation, the OPC- based concrete incurred mass losses of 2.41, 4.45, and 7.7 when exposed to fire at 200, 500, and 1000 °C, respectively. Similarly, when exposed to fire at 200, 500, and 1000 °C, the FA-based concrete had minor mass losses of 1.4, 1.96, and 2.59, respectively. According to the TGA analysis, the weight loss of geopolymer concrete was slightly higher than that of OPC up to 400 °C due to evaporation of water from the sample. At higher temperatures, the total weight loss of OPC is 6.1 whereas geopolymer is 4.5, indicating that geopolymer concrete was more chemically stable than OPC following exposure to high temperature fire. © 2024, Institute of Technology PETRONAS Sdn Bhd.