Abstract <p>Researches had explored the effect of family invalidation on social anxiety in adulthood, but little attention was paid to investigating the mediating mechanisms behind this relationship. The aim of this study was to examine whether adult attachment and loneliness played a mediating role between family invalidation and social anxiety among Chinese undergraduates. A total of 881 undergraduates were recruited to participate in our study and completed demographic information, Family Invalidation Scale, Adult Attachment Questionnaire, Loneliness Scale and Social Anxiety Scale. Mediation analysis revealed that attachment-related anxiety, attachment avoidance, and feelings of loneliness served as partial mediators in the relationship between family invalidation and social anxiety. Moreover, the chain mediating effect involving both attachment styles and loneliness was a statistically significant predictor of social anxiety in students from dysfunctional family backgrounds. The findings will help us deeply understand the relationship between family invalidation and social anxiety, and provide guidance for effectively enhancing adult attachment and alleviating loneliness of university students.</p> Highlights <p>• The findings demonstrate family invalidation could directly affect the social anxiety of Chinese undergraduates, and also affected social anxiety through the mediating roles of adult attachment and loneliness, as well as through the chain mediating role of these two variables.</p> <p>• This study extends the examination of the effect of family invalidation on the demographic of Chinese college students, providing partial elucidation of the etiological pathways leading to social anxiety in this population.</p> <p>• The study further refines the theoretical framework of family invalidation posited by Linehan, elucidating the connection between such an environment and attachment-related loneliness and social anxiety in adults.</p>