Background This study aimed to investigate the practice of off-label prescribing in both in- and outpatient psychiatry practice. Methods One-hundred inpatient and 100 outpatient medical records from adult patients of an Australian psychiatry service from 2020 to 2021 were examined to determine the prevalence of off-label prescribing as defined by Therapeutic Goods Administration (TGA) indications, adherence to Royal Australian and New Zealand College of Psychiatrists (RANZCP) treatment guidelines, frequency of off-label prescription, and the quality of documentation and informed consent process. Results Most prescribing events in both in- and outpatient settings were either on-label or off-label but consistent with RANZCP guidelines. Patients with a schizoaffective disorder diagnosis or displaying aggression were most likely to receive off-label prescriptions. There was no significant difference between in- and outpatient groups in the quality of documentation or consent process. Conclusions In general, off-label prescribing across groups was common, but many decisions were then in line with RANZCP recommendations. That there is a discrepancy between clinical and regulatory bodies has implications for how off-label status is decided.