Psychological inflexibility mediates the relationship between fear of negative evaluation and psychological vulnerability

College students worldwide and in Turkey face many biopsychosocial spiritual and economic issues, in part due to developmental and contextual factors. Understanding these issues and their relationship with psychological inflexibility, which is the central concept to the Acceptance and Commitment Therapy (ACT), is an unexplored gap in the literature. Therefore, the aim of the present study is to examine the mediating and moderating roles of Psychological Inflexibility (PI) in the relationship between Fear of Negative Evaluation (FNE) and Psychological Vulnerability (PV), and to set an empirical ground for developing evidence-based research and practices based on ACT. The study group consisted of 389 undergraduate students studying in various departments of a mid-sized urban state university. Regression-based mediation and moderation testing procedures revealed that PI partially mediates the relationship between FNE and PV. Moderating role of PI on the same relationship was not verified. The present findings are deemed to be useful for understanding the relationships of these constructs and developing future mental health research and interventions to address biopsychosocial spiritual issues and enhance wellbeing especially from an ACT perspective.