In 2018, about 50 million people were affected with dementia and this number is forecasted to triple by 2050. An important way to “curb this tidal wave of dementia” is to prevent cognitive decline in high-risk groups such as older adults with mild cognitive impairment (MCI). Recent work has shown that the combination of PA and cognitive activity may have beneficial effects on older adults’ cognitive health, but studying new and effective ways to do so in older adults with MCI is highly needed and of primary interest in dementia prevention. An intergenerational program (IGP) might be a promising and innovative way, involving old and young generations together in one program to promote health behaviors in both. Although IGPs has been frequently used and studied, only a few have used it to promote PA and most of them lack a theoretical basis or do not sufficiently meet the target groups’ needs. This project will develop and evaluate a novel IGP for older adults with MCI and their grandchildren, aiming to primarily improve cognitive, physical and psychosocial health in older adults with MCI and secondary in children. A theoretical framework will be used together with a co-creation approach for the intervention development. After pilot-testing, the effects will be evaluated in an RCT (with control and intervention group), measuring cognitive (CANTAB), physical (accelerometry) and psychological health (questionnaires) on pre- and post-test in older adults and their grandchildren.