There is a growing body of research investigating the impact on mental health professionals of losing a patient through suicide. However, the nature and extent of the impact is unclear. This systematic review synthesizes both quantitative and qualitative studies in the area. The aim was to review the literature on the impact of losing a patient through suicide with respect to both personal and professional practice responses as well as the support received. A search of the major psychological and medical databases was conducted, using keywords including suicide, patient, practitioner, and impact, which yielded 3,942 records. Fifty‐four studies were included in the final narrative synthesis. Most common personal reactions in qualitative studies included guilt, shock, sadness, anger, and blame. Impact on professional practice included self‐doubt and being more cautious and defensive in the management of suicide risk. As quantitative study methodologies were heterogeneous, it was difficult to make direct comparisons across studies. However, 13 studies (total n = 717 practitioners) utilized the Impact of Event Scale, finding that between 12% and 53% of practitioners recorded clinically significant scores. The need for training that is focused on the impact of suicides, and the value placed upon informal support was often cited. The experience of losing a patient through suicide can have a significant impact on mental health professionals, both in terms of their personal reactions and subsequent changes to professional practice. The negative impact, however, may be moderated by cultural and organisational factors and by the nature of support available.