What is known and objective: To describe the pharmacological management of post-traumatic stress disorder (PTSD) by psychiatrists, with a focus on their use of clinical guidelines and the role of prazosin for nightmares. Methods: An online survey of Australian and New Zealand psychiatrists was conducted. Aspects included respondent demographics, familiarity and usage of guidelines for PTSD, and opinions on the safety and efficacy of prazosin for PTSD-associated nightmares. Results and discussion: A total of 157 responses were recorded, 106 of which were complete. The most frequently used guideline for PTSD management was over 10 years old and used by only 48% of respondents. Peer-reviewed scientific journals were the most common additional source used by psychiatrists to inform their practice. For the targeted treatment of nightmares, 35 different medications had been trialled by respondents. Prazosin had been prescribed by 86% of psychiatrists for PTSD-associated nightmares, with only 2% reporting it to be ineffective in reducing nightmare frequency and/or intensity. Psychiatrists who were familiar with prazosin-mentioning guidelines (P <.05) and those who more frequently treat patients with PTSD (P <.01) were most likely to have prescribed prazosin. What is new and conclusion: Psychiatrists generally do not rely on guidelines to inform the treatment of PTSD. Off-label prescription of prazosin for PTSD-associated nightmares occurs frequently, with positive perceived outcomes, despite conflicting published evidence and a lack of local guideline recommendations for its use.