Background: Child maltreatment (CM) includes neglect, and several types of abuse, including physical, emotional, and sexual. CM has been associated with a wide range of mental illnesses. Literature examining these illnesses in mid-life is scarce, and the impact of these illnesses on mental health service use is currently unknown. Objective: To examine associations between self-reported CM and subsequent hospital admissions for mental illnesses, and/or community mental health service contacts. Setting: Birth cohort study data linked to administrative health data, including hospital admissions and community mental health service contacts, up to the age of 40. Methods: Associations between hospital admissions for mental health and community mental health contacts and CM subtypes (neglect, physical abuse, emotional abuse and sexual abuse) were examined using multivariate logistic regression. Results: Adjusted analyses showed that all subtypes of CM were significantly (p < 0.05) associated with admissions to hospital for any type of mental illness (aOR range 1.87–3.61), non-psychotic mental disorders (aOR range 1.98–3.61), alcohol and/or substance use (aOR range 2.83–5.43), and community mental health service contacts (aOR range 2.44–3.13). Hospital admissions for psychotic mental disorders were significantly associated with physical abuse, emotional abuse, and sexual abuse (aOR range 2.14–3.93). Conclusions: The results of this study confirm the current knowledge around CM and subsequent mental health illnesses up to the age of 40, and extend this knowledge to hospital and mental health service use.