Introduction: Technology-mediated strategies have potential to engage patients in modifying unhealthy behaviour and improving medication adherence to reduce morbidity and mortality from cardiovascular disease (CVD). Furthermore, electronic tools offer a medium by which consumers can more actively navigate personal healthcare information. Understanding how, why and among whom such strategies have an effect can help determine the requirements for implementing them at a scale. This paper aims to detail a process evaluation that will (1) assess implementation fidelity of a multicomponent eHealth intervention; (2) determine its effective features; (3) explore contextual factors influencing and maintaining user engagement; and (4) describe barriers, facilitators, preferences and acceptability of such interventions. Methods and analysis: Mixed-methods sequential design to derive, examine, triangulate and report data from multiple sources. Quantitative data from 3 sources will help to inform both sampling and content framework for the qualitative data collection: (1) surveys of patients and general practitioners (GPS); (2) software analytics; (3) programme delivery records. Qualitative data from interviews with patients and GPS, focus groups with patients and field notes taken by intervention delivery staff will be thematically analysed. Concurrent interview data collection and analysis will enable a thematic framework to evolve inductively and inform theory building, consistent with a realistic evaluation perspective. Eligible patients are those at moderate-to-high CVD risk who were randomised to the intervention arm of a randomised controlled trial of an eHealth intervention and are contactable at completion of the follow-up period; eligible GPS are the primary healthcare providers of these patients. Ethics and dissemination: Ethics approval has been received from the University of Sydney Human Research Ethics Committee and the Aboriginal Health and Medical Research Council (AH&MRC) of New South Wales. Results will be disseminated via scientific forums including peer-reviewed publications and national and international conferences.