Background <p>Interstitial lung disease (ILD) has a profound impact upon health-related quality of life (HRQoL) and mortality. Patients with ILD have identified their desire for tools to improve self-management. This study compares the clinical efficacy and cost-effectiveness of delivering an ILD-specific self-management package through a mobile health smartphone application (the REBUILD app), with standard care. It also evaluates the barriers and facilitators to adoption of the intervention in clinical practice.</p> Methods <p>This is a prospective, multicentre, randomised control trial (RCT) with embedded economic and implementation evaluations, with recruitment via ILD clinics at four Australian tertiary hospitals. Participants are allocated 1:1 to intervention and control groups, with randomisation stratified by disease severity, diagnosis, and site. The intervention group receives the self-management package and four phone health coaching sessions over 12 weeks. The control group receives standard care and four phone calls to control for attention. Outcomes will be measured at 12, 26 and 52 weeks. The primary outcome is change in HRQoL at 12 weeks, measured by the King’s Brief Interstitial Lung Disease questionnaire.</p> Discussion <p>Enhanced self-management has been associated with better HRQoL in several chronic respiratory conditions, however its effect in people with ILD is not known. This is the first multicentre RCT to evaluate the effect of a digital self-management intervention delivered through a smartphone app in people with ILD. If successful, this intervention has the potential to enhance access to self-management support for people with ILD.</p> Trial registration <p>This project was prospectively registered with the Clinical Trial Registry (NCT06122233||<a href="https://www.clinicaltrials.gov">https://www.clinicaltrials.gov/</a>/{08/11/2023}}.</p>