BACKGROUND: Despite the need to incorporate seniors from various settings into mindfulness-based empirical research, issues of geriatric frailties and non-compliance remain. This study aimed to evaluate the effects of a mindfulness-based elder care (MBEC) program on mental health and spiritual well-being among seniors with disabilities in long-term care residential settings. METHODS: This single-blind, randomized controlled trial (RCT) randomly assigned seventy-seven participants into an MBEC group or control group of an eight-week MBEC program. Participants were assessed every four weeks at baseline (T RESULTS: Linear mixed model (LMM) showed that MBEC participants' mental health improved significantly after completing the intervention; compared with controls, the MBEC group exhibited significantly lower anxiety (state-anxiety at T CONCLUSIONS: MBEC has positive effects on both mental health and spiritual well-being outcomes among seniors with disabilities. In long-term care facilities, seniors with abilities have the potential to adhere to and engage in activities of a mindfulness-based intervention. This low risk, easily accessible, and effective 8-week program is recommended to be integrated into regular long-term care institutional routines. TRIAL REGISTRATION: This study was registered with Clinical Trial Registry (ClinicalTrials.gov - U.S. National Library of Medicine #NCT05123261. Retrospectively registered on 07/04/2021.). The CONSORT 2010 guidelines were used in this study for properly reporting how the randomized trial was conducted.