This study examines the complex effects of empathic concern on mental health and behavioral manifestations and the potential indirect paths through excessive adaptation. A cross-sectional design with 1355 participants was employed. Empathic concern, excessive adaptation, prosocial behaviors, reactive aggression, depression, and positive mental health were assessed using established scales. Structural equation modeling and Bayesian linear regression were applied to analyze the paths. For direct paths, empathic concern positively predicted prosocial behaviors and positive mental health, whereas it was negatively related to depression and reactive aggression. For indirect paths, excessive adaptation was found to mediate the relationship between empathic concern and the outcome variables with the exception of positive mental health. By elucidating the mediating role of excessive adaptation, the results herein not only deepen our understanding of the dual effect of empathic concern on mental health and behavioral manifestations but also offer important insights for the medical and educational fields.