Mental health nurse are frequently subjected to patients' violent and aggressive behaviour. These assault experiences have given rise to mental health nurses' physical and psychological trauma, and negatively impact the quality of patient care. The purpose of the present qualitative study was to understand mental health nurses' experiences of being assaulted, the influences on their patient care, and their perspectives of the effectiveness of in-service, violence-prevention education. Ten mental health nurses from two different inpatient mental health facilities were interviewed using a semistructured interview guide. Thematic analysis of interview data found six themes: (i) violence is unpredictable; (ii) violence is normal; (iii) lasting psychological trauma; (iv) limited support from peers and the administrator; (v) violence prevention requires team cooperation; and (vi) doubting the effectiveness of in-service education on violence prevention. Psychiatric ward administrators should assess nurses' learning and skill needs to determine whether these needs are met by existing in-service training programmes. A culture of safety should also be promoted by building a warm and supportive ward climate for both staff and patients, which would include team cooperation and support for colleagues who suffer a violent incident.