This study is aimed at investigating the specific heat of fly-ash concrete. The experiments were conducted to obtain the specific heat of fly-ash cement pastes and mortars. Mortars were prepared by varying the sand type and content. It was found that the specific heat decreases as the amount of free water content decreases. The replacement of cement by fly ash resulted in high specific heat at young age but it tends to decrease in the long term due to the pozzolanic reaction. Mortars had lower specific heat than cement pastes. We propose a model for predicting the specific heat of concrete as a function of time, material, and mix proportion. The model, which was verified with various experimental results, simulated the trend of specific heat quite well.