Introduction: Digital health tools are frequently promoted as solutions to healthcare inequities, yet underserved populations often experience lower adoption, poorer engagement, and limited benefit. Co-design and participatory approaches—where patients, communities, and clinicians actively shape digital health solutions—may improve relevance and impact but have not been systematically evaluated. This systematic review examines how co-designed digital health interventions for underserved populations influence technology adoption, patient engagement, and clinical outcomes.

Methods: We systematically searched PubMed, Embase, CINAHL, PsycINFO, and IEEE Xplore for studies published between January 2010 and November 2025. Eligible studies (1) involved digital health interventions (e.g., telehealth, mobile apps, patient portals, remote monitoring); (2) explicitly targeted underserved populations (e.g., racial/ethnic minorities, rural, low-income, limited English proficiency); and (3) used co-design, participatory design, or community-based approaches in development. Two reviewers independently screened studies, extracted data, and assessed quality following PRISMA guidelines. Outcomes included measures of adoption, engagement, satisfaction, and clinical or behavioral outcomes.

Results: Of 863 records, 23 studies met the inclusion criteria. Co-designed interventions most frequently targeted chronic disease management, mental health, and maternal–child health. Studies reporting detailed co-design processes (e.g., iterative prototyping, community advisory boards, bilingual interfaces, culturally grounded content) demonstrated higher adoption and sustained engagement compared with top–down implementations in similar populations. Several interventions showed clinically meaningful improvements in glycemic control, depressive symptoms, medication adherence, and appointment attendance. However, the reporting of design methods and equity-related outcomes was highly variable, and few studies evaluated scalability or long-term sustainability.

Conclusions: Co-designed digital health interventions show promise for improving adoption, engagement, and selected clinical outcomes among underserved populations. Standardized reporting of co-design processes, explicit equity metrics, and rigorous evaluation of long-term implementation are needed to guide future digital health innovation that is genuinely patient-centered and inclusive.