Abstract Background Centralised specialist remote support, in which a clinician responds promptly to biomarker changes, could potentially improve outcomes in heart failure. The SUPPORT-HF2 trial compared telehealth technology alone with the same technology combined with centralised remote support. The intervention was implemented differently in different sites; no significant impact was found overall. We sought to explain these findings in a qualitative evaluation. Methods 51 people (25 patients, 3 carers, 18 clinicians and 4 additional research staff) were interviewed and observed in 7 SUPPORT-HF sites across UK between 2016 and 2018. We also collected 110 pages of documents. Analysis was informed by sociotechnical theory. Results Patients’ experiences of the technology were largely positive; staff engaged with the intervention to a variable degree. Existing services, staffing levels, technical capacity and previous experience with telehealth all influenced how the complex intervention of ‘telehealth technology plus centralised specialist remote support’ was interpreted and the extent to which it was adopted and used to its full potential. In some settings, the intervention was quickly mobilised to fill significant gaps in service provision. In others, it was seen as usefully extending the existing care model for selected patients. However, in some settings, the new care model was actively resisted and the technology little used. In one setting, centralised provision of specialist advice aligned awkwardly with an existing community-based heart failure support service. Conclusions The introduction of a telehealth programme rests not only on the technological intervention but also on the individuals involved and numerous subtle aspects of local service design. An iterative approach that attends to patients’ illness experiences, clinicians’ professional values, work practices and care pathways could lead to more effective telehealth support for patients with heart failure.