Background <p>Rheumatoid arthritis (RA) is a chronic autoimmune disease that requires long-term management and active self-care. In this context, emerging technologies—particularly mobile health applications—have demonstrated considerable potential in facilitating and enhancing self-care among patients with RA. This study aims to design, implement, and evaluate the effectiveness of a mobile-based self-care application to improve self-management in individuals with RA.</p> Methods <p>This study employs a sequential exploratory mixed-methods design with three phases, conducted in Sanandaj, Kurdistan Province, West Iran. In the qualitative phase (4 months), a conventional content analysis approach will be used to explore self-care experiences, needs, barriers, and facilitators among patients with RA. Data will be collected through semi-structured interviews using purposive maximum-variation sampling until saturation is reached. The data will be analyzed using the Graneheim and Lundman method to extract categories. In the development phase (8 months), the Nominal Group Technique (NGT) will be conducted with a multidisciplinary expert panel to refine, enrich, and prioritize the identified needs and define the mobile application’s content. Software development will follow the Waterfall Model. Usability and user satisfaction will be evaluated through expert reviews and a pilot study involving 30 patients. In the quantitative phase (4 months), a Randomized Controlled Trial (RCT) will assess the application’s effectiveness. Seventy-two RA patients will be randomly assigned to intervention (<i>n</i> = 36) or control (<i>n</i> = 36) groups. Both groups will receive routine care, while the intervention group will additionally use the application for 8 weeks. Outcomes include self-care levels, quality of life, and disability index. Ethical and administrative approvals were obtained prior to study commencement.</p> Discussion <p>This study investigates the impact of a mobile-based self-care application on improving self-care behaviors and disease management among patients with RA. The design and implementation of this application are expected to enhance patient experiences, promote self-care, and reduce negative disease outcomes, while also improving quality of life and lowering the disability index.</p> Trial registration <p>IRCT, IRCT20100913004736N30. Registered on 2 October 2025 and approved by the Ethics Committee of Kermanshah University of Medical Sciences ((IR.KUMS.REC.1403.603)). Available at: <a href="https://irct.behdasht.gov.ir/search/result?query=IRCT20100913004736N29">https://irct.behdasht.gov.ir/search/result?query=IRCT20100913004736N29</a>.</p>