The PHASE research programme is an NHS-Executive funded, randomized controlled trial of assisted self-help for common mental disorders, delivered by practice nurses in primary care. The self-help guide – Managing anxiety and depression: a self-help guide published by the Mental Health Foundation – is conceptualized as a ‘health technology’ where the nurse's role is to educate patients how to get the best out of the technology, supervise its safe delivery and monitor its continued use by patients so that they can use it independently with little reliance on nurses or other health professionals. Twenty-three nurses were trained on one of five, 3-day courses to deliver PHASE. As the final task during the training course, nurses were asked to describe what they would say to a patient when delivering PHASE. From these data a qualitative thematic content analysis was used to develop a coding framework which showed that nurses were able to articulate a sophisticated health technology rationale, including relevant psychological models and the principle of an evidence base. This study demonstrates that it is possible to equip primary care nurses with both a highly developed understanding and the knowledge to deliver self-help mental health care. Training nurses using this model moves us away from traditional mental health training courses that have attempted to produce ‘watered down’ versions of specialist practitioners to a more appropriate skills and cultural ‘health technology’ fit for delivering primary mental health care.