This paper presents the effect of temperature on the fatigue properties of carbon steel containing three different content of carbon: 0.758%C, 0.539%C and 0.319%C. The tests were conducted at room temperature and at variable temperatures. The temperature cycle used was in the range from 50oC to 100oC and 150oC respectively. Using constant amplitude loading, the fatigue test was done by rotating bending machine. The results obtained from the fatigue test at room temperature were compared with the fatigue test results at variable temperatures. A modified Miner rule was applied to predict the fatigue life at variable temperatures and to evaluate the fatigue damage in every steel alloy. The fatigue damage was determined as the number of cycles and stress. The results showed that the alloy steel with 0.539%C had the best resistance to the constant applied load and variable temperature and it was also found that the fatigue life of all three alloys decreased at variable temperature compared to room temperature.