Empirically, mental health and mental illness are not opposite ends of a single measurement continuum. In view of this fact, Keyes ("J Health Soc Behav," 43:207-202, 2002) operationalizes mental health as a syndrome of symptoms of both positive feelings (emotional well-being) and positive functioning (psychological and social well-being) in life. In his comprehensive model, the presence of mental health is described as flourishing in life, and the absence of mental health is characterized as languishing in life. The aim of this study was to investigate the discriminatory power of Big Five personality traits in discriminating among the levels of mental health continuum using an Iranian university student sample. Findings revealed that respondents with different levels of mental health differed significantly on four of the five personality traits (extraversion, neuroticism, conscientiousness, and agreeableness). All in all, the results of this study converged with prior findings about the importance of Big Five personality traits in predicting well-being.