Background. Deliberate self-harm is frequently encountered by emergency department (ED) nurses. However, clients are often dissatisfied with the care provided and clinicians feel ambivalent, helpless or frustrated when working with clients who self-harm. Aim. The aim of the study was to develop and test a scale to identify relevant dimensions of ED nurses' attitudes to clients who present with self-injury. Methods. Items on Attitudes Towards Deliberate Self-Harm Questionnaire (ADSHQ) were drawn from a literature review and focus group discussions with ED nurses. The tool was piloted with 20 ED nurses not working in the target agencies. A survey of nurses working within 23 major public and 14 major private EDs in Queensland, Australia (n = 1008) was then undertaken. Results. A total of 352 questionnaires were returned (35% response). Analysis revealed four factors that reflected nurses' attitudes toward these clients. The factors related to nurses' perceived confidence in their assessment and referral skills; ability to deal effectively with clients, empathic approach; and ability to cope effectively with legal and hospital regulations that guide practice. There was a generally negative attitude towards clients who self-harm. Correlations were found between years of ED experience and total score on the ADSHQ, and years of ED experience and an empathic approach towards clients who deliberately self-harm. Conclusion. There is a need for continuing professional development activities to address negative attitudes and provide practical strategies to inform practice and clinical protocols.