 New approaches to control healthcare expenditures and increase access to quality care are required by decision-makers in high-income countries. One strategy is to reallocate tasks from doctors to nurses. Evidence suggests that quality, effectiveness and efficiency of task shifting are context sensitive and affected by implementation. However, little is known about implementability of task shifting in specialised healthcare. We aimed to identify factors perceived to influence implementation of doctor-to-nurse task shifting in a hospital setting and improve understanding of task shifting implementability by using theory-based frameworks for analysing behaviour. Nurse-led bone marrow examination exemplified task shifting from the medical to the nursing domain.