BACKGROUND: Guidelines recommend cardiac rehabilitation and long-term use of cardiac medications for most patients who have had a myocardial infarction (MI), but adherence to these secondary prevention treatments is suboptimal. METHODS: This is a multicenter, pragmatic, 3-arm randomized trial. Eligible patients (n = 2,742) with obstructive coronary artery disease are randomized post-MI to usual care or 1 of 2 intervention arms. Patients in the first intervention arm receive mail-outs sent on behalf of their cardiologist at 4, 8, 20, 32, and 44 weeks post-MI; content is designed to address determinants of adherence and facilitate discussion between the patient and their health care team. Patients in the second intervention arm receive mail-outs plus automated interactive voice response system telephone calls 2 weeks after each letter, as well as a telephone call by trained lay health workers if the interactive voice response system identifies challenges with adherence. Outcomes are assessed 12 months post-MI via patient self-report and administrative data sources. Co-primary outcomes are adherence to cardiac medications and completion of cardiac rehabilitation. Secondary outcomes include cardiovascular events and mortality. An embedded, theory-informed process evaluation will explore the mechanism of action; an economic evaluation is also planned. CONCLUSIONS: We describe a complete program evaluation of a highly pragmatic, health-system intervention to support adherence to recommended treatments. Research ethics boards approved waiver of consent for patients enrolled in the trial with provision of multiple opportunities to opt out and a debrief at the time of outcome assessment. The methods used here may provide a model for similar interventions.