In this study, the thermal behaviors of the athlete’s bodies were investigated with respect to thermal comfort and exercise intensity experimentally. The relation between Predicted Mean Vote (PMV) which is an thermal comfort index and Ratings of Perceived Exertion (RPE) that measures the exercise intensity and exhaustion level was evaluated statistically. The experiments were carried out with eleven subjects in a conditioned test chamber at School of Physical Education and Sports in Ege University with a bicycle ergometer in 2012 and 2013. The relation between PMV and RPE was analyzed statistically by SPSS and the average correlation coefficient was obtained -0,52. This result mentions that there are a negative moderately correlation. Moreover, the oxygen consumption rate and core body temperature which affect the exercise performance of athletes were divided two groups as high and low and statistically analysis were conducted. Accordingly, while the average correlation coefficient at high oxygen consumption rate group decreases -0,21, the average correlation coefficient at low oxygen consumption rate group increases -0,77. The level of correlation coefficient decreases at the subjects whose oxygen consumption rates are high. Similarly, while the average correlation coefficient at high core body temperature group decreases -0,36, the average correlation coefficient at low core body temperature group increases -0,70. The existed level of correlation coefficients increases at the subjects whose core body temperatures are low.