Background and Objectives: Family caregivers of people with dementia (PWD) experience high levels of stress resulting from caregiving. This study aimed to investigate the effects of a modified of Mindfulness-Based Cognitive Therapy (MBCT) for dementia caregiving. Research Design and Methods: 113 family caregivers of PWD were randomized to either the intervention group, receiving the 7-session modified MBCT for a period of 10 weeks with telephone follow-up or the control group, receiving the brief education on dementia care and usual care. The caregiving stress (primary outcome) and various psychological outcomes of caregivers and the behavioral and psychological symptoms of dementia (BPSD) in the care recipients were assessed and compared at baseline (T0), postintervention (T1), and at the 6-month follow-up (T2). Results: At both T1 and T2, the intervention group had a statistically greater improvement in stress (p = .02 and .03), depression (p = .001 and .04), anxiety (p = .007 and .03), and BPSD-related caregivers' distress (p = .003 and p = .04). A significant greater improvement was also demonstrated in mental health-related quality of life at T2 (p = .001) and BPSD of the care recipients at T1 (p = .04). The increased caregivers' level of mindfulness was significantly correlated with the improvement of various psychological outcomes at T1 and T2 with a correlation coefficient −0.64 to 0.43. Discussion and Implications: The modified MBCT enhanced the level of mindfulness in the caregivers and was effective to reduce the caregivers' stress and promote their psychological well-being during a 6-month follow-up. Future research is recommended to further examine its effects on the varieties of psychological and behavioral outcomes of both caregivers and care recipients and their dyadic relationships, as well as explore its mechanism of action in facilitating dementia caregiving.