Background <p>Increasing numbers of persons with dementia are cared for at home by informal caregivers, underscoring the need for caregiver support. This study evaluated the MOMANT intervention: a psychosocial training programme for informal caregivers consisting of 6 group sessions led by healthcare professionals covering education on dementia, managing changes in behaviour and communication, and coping with caregiver burden. In addition, informal caregivers were trained to actively engage the person with dementia in stimulating activities at home. The primary aim was to improve the quality of life for both the informal caregiver and the person with dementia.</p> Methods <p>This randomised controlled trial compared outcomes in 172 dyads (<i>n</i> = 74/43% intervention, <i>n</i> = 98/57% control continuing usual care). Training took place in small groups led by healthcare professionals at Dutch dementia daycare and Meeting Centres. Randomisation occurred at the centre level. Participants were assessed at baseline and at 3- and 6-month follow-up. Outcomes included [instrumental] activities of daily living ([I]ADL) dependency, global functioning, and activity engagement (person with dementia only); sense of competence, caregiving experiences, and mood (caregiver only); quality of life and healthcare usage (both). Caregivers and healthcare professionals also evaluated the intervention in surveys. Outcomes were analysed over time using longitudinal mixed models (intention-to-treat), with group by time interaction (control as reference), α = 0.05. Subsequently, effects between intervention and control groups were compared at 3 and 6 months.</p> Results <p>Longitudinal mixed models showed no significant interactions for most outcomes, indicating that the trajectories of the outcomes of the intervention and control groups did not differ over time (<i>p</i>’s &gt; .05). However, compared to the control group, persons with dementia in the intervention group engaged in more activities (t=-2.38, <i>p</i> = .02), and caregivers in the intervention group reported more positive caregiving experiences (t=-2.16, <i>p</i> = .03) at the 3-month follow-up. Subjective evaluations of the intervention were positive: caregivers considered the content useful and reported improved dyadic interactions.</p> Conclusion <p>This study demonstrates the potential of a psychosocial caregiver-led intervention to increase activity engagement of the person with dementia and enhance positive caregiving experiences. Although most outcomes showed no significant changes, positive evaluations of the intervention highlighted the benefits of information, emotional support, and practical training for informal caregivers.</p> Trial registration <p>The trial was registered at the Dutch Trial Register (NTR6643) August 22nd, 2017.</p>