This study aimed to find out the relationship between transformational leadership and athletic performance through a series of two studies. In Study 1, we tried to find out whether the relationship between transformational leadership and athletic performance can be significantly mediated by intrateam communication. In study 2, we tried to find out if the mediating effect of study 1 was differently moderated by team cohesion. The participants of study 1 were 300 high school kumdo players, and study 2 was 232 university and professional team players. The participants were sampled using purposive sampling. All measurement tools used in this study were produced through standardized procedures, and tools with proven validity and reliability were used. For the data processing of this study, SPSS 18.0, AMOS 18.0, and PROCESS Macro statistical programs were used to perform factor analysis, reliability analysis, correlation analysis, mediating effect, and moderation effect analysis. Through the above analysis, the following major findings were obtained. First, transformational leadership had a positive effect on athletic performance, but there was no statistical significance. Second, transformational leadership had a significant effect on intrateam communication. Third, intrateam communication had a significant effect on athletic performance. Fourth, transformational leadership had a significant indirect effect on athletic performance through intrateam communication. Fifth, transformational leadership had a positive effect on athletic performance. Sixth, transformational leadership caused negative indirect effects on athletic performance through overall intrateam communication, distinctiveness, and negative conflict communication, and significant positive indirect effects through acceptance and positive conflict. Seventh, the mediating effect of transformational leadership→intrateam communication→athletic performance had different moderating effects depending on the level of team cohesion. 1)The negative indirect effect of charismatic transformational leadership on athletic performance through distinctiveness communication was different according to the conditions of group integration-task cohesion. 2)The indirect effect of charismatic transformational leadership on athletic performance through acceptance communication was different according to the conditions of group integration-social cohesion. 3)The indirect effects of charismatic transformational leadership on athletic performance through distinctiveness communication were different according to the conditions of group integration-task cohesion. 4)The indirect effect of charismatic transformational leadership on athletic performance through distinctiveness communication was different according to the conditions of group integration-social cohesion. 5)The indirect effect of inspirational motivation on athletic performance by through distinctiveness communication was different according to the conditions of individual attractions to group-task cohesion. 6)The indirect effect of inspirational motivation on athletic performance through positive conflict communication was different according to the conditions of group integration-social cohesion. 7)The indirect effect of inspirational motivation on athletic performance through negative conflict communication was different according to the condition of individual attraction to group-task cohesion. 8)The indirect effect of inspirational motivation on athletic performance through negative conflict communication was different according to the conditions of individual attractions to group-social cohesion.