In contrast to conventional definitions, the contemporary conceptualization of adulthood emphasizes psychological characteristics over sociodemographic milestones. At the same time, an increasing number of theorists propose that the way individuals view adulthood may have a significant impact on the mental health of both adolescents and adults. However, empirical examination of this hypothesis has been notably limited to date. The aim of this study is to explore the association between individuals' perceptions of adulthood and multiple dimensions of mental health. This study applied some adulthood markers and multiple mental health indexes (including well-being, optimism, Alexithymia, satisfaction with life, Goldberg's index of mental health, the dark triad, and dimensional personality disorders) to a community sample comprising 1772 individuals in Spain, spanning ages from 16 to 93 years. The findings support the overarching hypothesis, as perceptions of adulthood display strong correlations with nearly every assessed index of mental health, particularly those that comprise a dimension of negative emotions. These associations persist even after accounting for age and socio-economic status, and in alignment with the psychological paradigm of adulthood, they show a notable consistency across various age groups. This study establishes that such perceptions of adulthood represent a modifiable factor contributing to positive mental health. The implications of these findings for the formulation of public policies aimed at promoting mental health in the context of adulthood, as well as a number of future studies, are deliberated.