The purpose of this study was to examine the relationships between personality, coping, social support, mental health, and psychological stress, in college athletes. We developed a conceptual diagram based on the psychological stress theory of Lazarus and Folkman (1984) and tested this diagram having personality as an independent variable and mental health as a dependent variable. Stress coping behavior and social support were also included in the diagram as mediating variables because they were conceptualized as being affected by individual personality. One hundred and eighty-six college athletes (115 males, 71 females) participated in the study, and completed three questionnaires: (a) the Tokyo University Egogram (TEG), which assessed personality; (b) an athletic stress coping behavior scale and athletic social support scale; and (c) the Mental Health Pattern. The TEG is a questionnaire developed based on transactional analysis theory that assesses the five ego states: Critical Parent, Nurturing Parent, Adult, Free Child, and Adapted Child. The collected data were analyzed using structural equation modeling, and the model showed a good fit to the data (GFI=.967, AGFI=.983, CFI=.959, RESEA=.074). The results indicated that personality was directly related to mental health. For example, Adapted Child, as measured by the TEG, was directly related to the participants' stress responses. The results also indicated that personality was indirectly related to mental health through its effects on coping and social support. For quality of life, Free Child was more influential than the other ego states. In addition, individuals were more likely to utilize problem-focused coping, emotion-focused coping, and social support in order to improve their quality of life. The results of this study suggest that stress management education corresponding to each personality type may be useful for maintaining the mental health of college athletes and facilitating their quality of life.