Carbon fiber reinforced polymer (CFRP) has been used widely in strengthening of steel structures. Steel/CFRP systems subjected to elevated temperatures is realistic in a summer climate event in many countries where the temperature in steel may approach 50 °C or even higher, which will lead to the degradation of the bond performance between CFRP and steel. Therefore, predicting the bond behavior of the CFRP/steel system under elevated temperature is critical. This paper investigated the mechanical performance of CFRP/steel adhesively-bonded double strap joints at elevated temperatures. Thirty CFRP-steel double strap joints were tested to failure under temperatures between 10 °C and 90 °C. It was found that the joint failure mode changed from adherend failure to debonding failure as the temperature approached T_g. In addition, the ultimate load and joint stiffness decreased significantly at temperatures near to and greater than T_g. Based on the experimental results, a model is proposed to predict the bond stress of the CFRP/steel at different temperatures.