Advance care planning (ACP) allows patients to express and document their preferences about medical treatment; however, there are concerns about uptake and documentation due to human error. This study used patient safety incident reports in the UK to characterize and explore safety issues arising from ACP and to identify areas for improvement. Over a ten-year period, there were 70 reports of an ACP-related patient safety incident (due to incomplete documentation, inaccessible documentation or miscommunication, or ACP directives not being followed) which led to inappropriate treatment, transfer or admission. The importance of targeting the human factors of the ACP process to improve safety is discussed. The PSNet Human Factors Engineering primer expands on these concepts.