Background: Trial participant recruitment is an interactional process between health care professionals, patients and carers. Little is known about how clinicians carry out this role in palliative care trials and the reasons why they do or do not recruit participants. Aims: To explore how clinicians recruit to palliative care trials, why they choose to implement particular recruitment strategies, and the factors that influence their choices. Design: A qualitative multiple case study of three UK palliative care trials. Data collection included interviews and study documentation. Analysis involved developing and refining theoretical propositions, guided by the ‘6Ps’ of the ‘Social Marketing Mix Framework’ as an a priori framework (identifying participants, product, price, place, promotion and working with partners). Framework Analysis guided within and then cross-case analysis. Settings/participants: Study investigators and research staff (n = 3, 9, 7) from trial coordinating centres and recruitment sites (hospice and hospital). Results: Cross-case analysis suggests the ‘Social Marketing Mix Framework’ is useful for understanding recruitment processes but wider contextual issues need to be incorporated. These include the ‘emotional labour’ of diagnosing dying and communicating palliative and end-of-life care to potential participants and how the recruitment process is influenced by the power relationships and hierarchies that exist among professional groups. These factors can lead to and support paternalistic practices. Conclusions: Those planning trials need to ensure that trial recruiters, depending on their experience and trial characteristics, have access to training and support to address the ‘emotional labour’ of recruitment. The type of training required requires further research.