ObjectivesPatients with chronic conditions enrolled in high-deductible health plans (HDHPs) face cost-related access barriers and high out-of-pocket spending. Our objectives were to develop a novel behavioural intervention to help HDHP enrollees with chronic conditions use cost-conscious strategies and evaluate the intervention’s preliminary effectiveness, acceptability and feasibility.DesignProspective.SettingOnline (USA).Participants36 US adults enrolled in an HDHP through their employer or an exchange with diabetes, hypertension, asthma, coronary artery disease and/or chronic obstructive pulmonary disease. 31/36 participants completed the study.InterventionWe developed a 5-week intervention consisting of a website with educational modules on discussing costs with clinicians, saving for future healthcare costs, comparing healthcare prices and quality, preparing for appointments, following up after appointments and planning for future healthcare needs; and emails encouraging participants to access each module.OutcomesWe conducted a single-arm proof-of-concept pilot study of the intervention. Baseline and postintervention surveys measured primary outcomes of health insurance literacy and confidence in using cost-conscious strategies. 10 participants completed postintervention interviews.Results31 (86%) participants completed a baseline and postintervention survey. Mean health insurance literacy scores (20–80 scale) improved from 56.5 to 67.1 (p<0.001). Mean confidence scores (0–10 scale) improved for talking to a healthcare provider about cost (6.1–7.6, p=0.0094), saving for healthcare (5.8–6.6, p=0.068), comparing prices (5.4–6.9, p=0.005) and comparing quality (6.1 to 7.6, p=0.0034). Participants found the website easy to use and helpful for learning about cost-conscious strategies on postintervention interviews.ConclusionsOur novel behavioural intervention was acceptable to HDHP enrollees with chronic conditions, feasible to deliver and associated with increased health insurance literacy and confidence in using cost-conscious strategies. This intervention should be tested in a definitive randomised controlled trial that is fully powered to evaluate its effects on cost-related access barriers, out-of-pocket spending and health outcomes in this growing patient population.