<p>Adverse childhood experiences (ACEs) have been established as major risk factors for developing mental disorders across the lifespan. In contrast, positive childhood experiences (PCEs) have been shown to be associated with better mental health outcomes across different levels of ACE exposure. However, few studies have examined whether different types of PCEs—particularly family-based and community-based experiences—show distinct associations with adult mental health outcomes. This study aimed to examine whether family PCEs (FPCEs) and community PCEs (CPCEs) are independently associated with mental disorders in adulthood and whether these associations differ according to the level of ACE exposure. We conducted a cross-sectional analysis of 28,221 adults aged 18&#xa0;years and older from the 2023 wave of the Japan COVID-19 and Society Internet Survey (JACSIS). Mental disorders were assessed using a self-reported checklist of physician-diagnosed conditions. Logistic regression models were used to evaluate associations between ACEs, FPCEs, CPCEs, and mental disorders, adjusting for sociodemographic covariates. Among individuals with no ACEs, experiencing 3 or 4 CPCEs was associated with lower odds of mental disorders (AOR = 0.59, 95% CI: 0.48–0.73; AOR = 0.48, 95% CI: 0.39–0.60, respectively). In the one ACE group, 2–4 CPCEs were also associated with lower odds of mental disorders (AOR = 0.70, 95% CI: 0.53–0.93; AOR = 0.64, 95% CI: 0.46–0.88; AOR = 0.51, 95% CI: 0.35–0.75, respectively). In contrast, FPCEs were not significantly associated with mental disorders in any ACE category. CPCEs were associated with lower odds of adult mental disorders among individuals with zero or one ACE, whereas no such associations were observed among those with two or more ACEs. Our findings suggest that positive experiences outside the family environment may be relevant to adult mental health, although these associations appear to vary across levels of childhood adversity.</p>