<p>To test whether a 10-day mindfulness program delivered through the ŌURA app improves sleep and stress in healthy adults, eighty-one adults were randomized to mindfulness (n = 49) or waitlist control (n = 32). Participants wore an Ōura ring during baseline, intervention/wait-list, and 4-week follow-up, recording sleep efficiency, total, deep, and light sleep, plus sleep-onset time. Questionnaires—Pittsburgh sleep quality index (PSQI), perceived stress scale (PSS), Copenhagen burnout inventory (CBI), and mindful attention awareness scale (MAAS)—were completed pre- and post-intervention and at follow-up. Mixed-model ANOVAs revealed significant group × time interactions for sleep efficiency, total sleep, deep and light sleep, and sleep-onset time (all <i>p</i>s &lt; 0.031). Results showed that the mindfulness group improved after 10&#xa0;days (all <i>p</i>s &lt; 0.021); gains persisted at follow-up except for deep sleep. The mindfulness group exhibited increased personal burnout (<i>p</i> = 0.021) immediately post-intervention, though this returned toward baseline at follow-up. In addition, the mindfulness showed higher MAAS scores (<i>p</i> = 0.017). During mindfulness sessions heart rate fell (<i>p</i> = 0.011) and heart-rate variability rose (<i>p</i> = 0.029). A brief, app-based mindfulness program produced sustained improvements in sleep efficiency and enhanced HRV, demonstrating that digital mindfulness can favorably influence biobehavioral sleep-stress metrics.</p><p><i>Trial Registration</i>: ClinicalTrials.gov: NCT07469644</p>