Electroconvulsive therapy (ECT) has been applied in mental and general hospitals in the Netherlands since 1939, but we know little about nurses’ role in the transformation brought about by the ECT machine and its use. Based on archival documents, interviews and a case study of nurses’ work in ECT at the university hospital in the city of Groningen, this article shows how nurses’ professional identity was depicted and changed within the application and practice of ECT. Although nursing was an integral part of ECT practice from the outset, it was also affected and changed by it, especially as public debate and controversy over ECT arose in 1970s. During this time mental health grew as an interdisciplinary field, pressuring nurses to articulate their psychiatric nursing expertise. New governmental ECT guidelines in the 1980s also shaped nurses’ work. Once protest over ECT subsided in the 1990s, reflecting a new acceptance of biological psychiatry, use of ECT increased again and nurses obtained a specialized role in ECT. The article concludes that whereas nursing’s traditional close ties to medical knowledge and practice has been a source of professional tension, the connection also gave nurses new opportunities to renegotiate their expertise when the use of ECT increased during the 1990s. It realigned them with medicine in new ways, opening new professional avenues in specialized ECT nursing practice.