Adverse childhood experiences (ACEs) are common in people at clinical high-risk for psychosis (CHR), however, the relationship between ACEs and long-term clinical outcomes is still unclear. This study examined associations between ACEs and clinical outcomes in CHR individuals. 344 CHR individuals and 67 healthy controls (HC) were assessed using the Childhood Trauma Questionnaire (CTQ), the Bullying Questionnaire and the Childhood Experience of Care and Abuse (CECA). CHR were followed up for up to 5 years. Remission from the CHR state, transition to psychosis (both defined with the Comprehensive Assessment of an At Risk Mental State), and level of functioning (assessed with the Global Assessment of Functioning) were assessed. Stepwise and multilevel logistic regression models were used to investigate the relationship between ACEs and outcomes. ACEs were significantly more prevalent in CHR individuals than in HC. Within the CHR cohort, physical abuse was associated with a reduced likelihood of remission (OR = 3.64, p = 0.025). Separation from a parent was linked to an increased likelihood of both remission (OR = 0.32, p = 0.011) and higher level of functioning (OR = 1.77, p = 0.040). Death of a parent (OR = 1.87, p = 0.037) was associated with an increased risk of transitioning to psychosis. Physical abuse and death of a parent are related to adverse long-term outcomes in CHR. The counter-intuitive association between separation from a parent and outcomes may reflect the removal of a child from an adverse environment. Future studies should investigate whether interventions targeting the effect of specific ACEs might help to improve outcomes in this population.