Objectives <p>Studies consistently demonstrate that family caregivers often experience poor health, depression, anxiety, and a diminished quality of life. Mindfulness-based interventions have shown positive outcomes, and this study aimed to investigate the effects and mechanisms of a low-intensity mindfulness-based program for caregivers of frail older adults.</p> Method <p>A multi-site, three-arm randomized controlled trial was conducted to assess the impact of a mindfulness-based intervention for Chinese family caregivers. Intervention effects were compared with those of an evidence-based psychoeducation program and treatment-as-usual. One hundred and fifty-one caregivers initially expressed interest in participating, with 93 eligible caregivers ultimately being randomly assigned to the brief mindfulness-based program, psychoeducation, or treatment-as-usual.</p> Results <p>Caregivers in the mindfulness group showed greater improvements in depression, experiential avoidance, family functioning, self-efficacy, and problem-solving in coping style at post-intervention, compared with those receiving usual care. When compared to the psychoeducation group, caregivers in the mindfulness group showed greater improvements in experiential avoidance, and problem-solving coping. The improvement in self-efficacy was sustained at the 6-month follow-up.</p> Conclusions <p>The findings suggest that a brief mindfulness-based intervention can significantly enhance caregiver mental health and overall well-being. This study provides further evidence that a low-intensity mindfulness intervention could be better suited to address the challenges faced by caregivers with limited time due to their demanding schedule.</p> Preregistration <p>This study was preregistered with the United States Clinical Trials Registration (ClinicalTrial.gov) (NCT04861610).</p>