introductionCardiac rehabilitation (CR) can reduce cardiovascular mortality and improve health-related quality of life. In the United Kingdom, patient uptake of CR remains low (52%), falling well short of the target in the 2019 National Health Service long-term plan (85%). Mobile health (mHealth) technologies, offering biometric data to patients and healthcare professionals, may bridge the gap between supervised exercise and physical activity advice, enabling patients to engage in regular long-term physically active lifestyles. This randomised controlled trial (RCT) will evaluate the feasibility of mHealth technology when incorporated into a structured home-based walking intervention, in people with recent myocardial infarction. METHODS AND ANALYSIS: This is a feasibility, assessor blinded, parallel group RCT. Participants will be allocated to either CR standard care (control group) or CR standard care+mHealth supported exercise counselling (mHealth intervention group). Feasibility outcomes will include the number of patients approached, screened and eligible; the percentage of patients who decline CR (including reasons for declining), agree to CR and consent to being part of the study; the percentage of patients who enrol in standard CR and reasons for drop out; and the percentage of participants who complete clinical, physical and psychosocial outcomes to identify a suitable primary outcome for a future definitive trial. ETHICS AND DISSEMINATION: The trial was approved in the UK by the Northwest-Greater Manchester East Research Ethics Committee (22/NW/0301) and is being conducted in accordance with the Declaration of Helsinki and Good Clinical Practice. Results will be published in peer-reviewed journals and presented at national and international scientific meetings. TRIAL REGISTRATION NUMBERS: NCT05774587.