Background Childhood adversity impacts adult mental health, increasing the risk of internalising disorders such as anxiety and depression. Research indicates the potential role of negative schemas in mediating the relationship between adversity and adult mental health outcomes and suggests that positive schemas might play an additional role. Objective This study aimed to elucidate the mediating effect of positive schemas on the relationship between childhood adversity and adulthood internalising disorders. Methods An online questionnaire gathered data from 199 individuals aged over 18 from the UK general population. Information regarding childhood adversity, adult mental health, and positive schemas was collected. Simple mediation analyses were used to establish the mediation effect. Results The results showed that individuals exposed to multiple forms of childhood adversity had fewer positive schemas than individuals exposed to no adversity or a single form (P<0.05). Positive schemas mediated the relationship between childhood adversity and adulthood internalising disorders. In particular, low self-efficacy mediated the relationship between childhood adversity and anxiety, and low worthiness mediated the relationship between adversity and depression. Conclusions This study highlighted that in the context of childhood adversity, low self-efficacy creates vulnerability for anxiety and low worthiness for depression. Findings have implications for developing an individualised approach to understanding the personal meanings behind mental health presentations, and which could aid formulation and intervention approaches.