Objective: This study assessed levels of anxiety, depression, and stress among family caregivers of children and adolescents with mental disorders in Ghana and the implication on medication adherence. Design: A cross-sectional study. Setting: The study was conducted at the outpatient departments of the three main public psychiatric hospitals in Ghana. Participants: Two hundred and ten non-paid family caregivers of children and adolescents with mental disorders were recruited for this study. Main Outcome Measure: The study assessed symptoms of anxiety, depression and stress among the caregivers and estimated caregiver-reported medication adherence. Results: About 56.2%, 66.2% and 78% of the caregivers experienced severe anxiety, severe depression and moderate to severe stress symptoms respectively. From the multiple logistic regression model, while anxiety was significantly affected by religion and education, depression was influenced by sex, age, marital status, proximity to facility, and employment status. Female caregivers had about four times higher odds of being depressed compared to male caregivers (aOR: 3.81, 95% CI: 1.66 - 8.75). The caregiver-reported medication adherence was 11.9%. Anxiety was significantly predictive of medication adherence. Conclusion: Most family caregivers of children and adolescents with mental disorders experienced symptoms of anxiety, depression and stress with anxiety having implications for medication adherence. The study findings underscore the need to consider psychological characteristics of caregivers and the provision of mental health support for them, as part of the routine health care for children and adolescents with mental disorders.