Focusing on the argument of which assumed competence was derived from the motivation of self-enhancement for the ego-threatened person, the present study elucidated its relationship to anxiety, defense mechanism, subjective well-being, and hopelessness. In the first study, 354 undergraduates were classified into 4 competence types based on crossing scores of the Assumed Competence and Self-Esteem scales: atrophic, self-esteemed, omnipotent, and assumed. Those who were categorized in assumed competence type rated the highest on anxiety and coped with their ego-threat on immature defense level. In the second study, a self-report questionnaire was administered to 300 undergraduates to examine the relationships among assumed competence, self-esteem, subjective well-being, and hopelessness. The results clarified that their mental health varied not solely with a tendency of undervaluing others but with self-esteem. Discussed were some issues for future research in terms of training programs exerted to cope with ego-threats on mature defense level, to protect self-esteem, and then to improve well-being for adolescents.