Background Participation in physical activity represents a lifestyle modification that can potentially improve quality of life and well-being for people with young onset dementia (symptom onset before 65). This study aimed to explore perceptions, barriers and enablers of physical activity among people with young onset dementia and care partners. Methods Ten people (male, n = 6) aged 53-66 with young onset dementia (Including people with Alzheimer’s disease, frontotemporal dementia, Lewy body dementia, posterior cortical atrophy, and primary progressive aphasia) and nine care partners (female, n = 8) aged 55-67, participated in semi-structured interviews. Interviews data were analysed using reflexive thematic analysis. Results Five overarching themes were identified: 1) Safe participation in physical activity. Care partners expressed concerns for safe exercise participation and noted the need for activity modification with disease progression. 2) Social inclusion and community participation. People sought group-based and dementia inclusive activities to combine social interaction and physical activity. 3) The impact of a dementia diagnosis on physical activity and wellbeing. Physical activity can mitigate the loss of sense of self and independence experienced post-diagnosis. 4) There is a need to overcome systemic and accessibility challenges, such as limitations in transport accessibility. 5) The role of tailored activity design. Discussion To effectively encourage physical active lifestyles and design exercise programs for people with young onset dementia, their distinct contexts need to be considered. Group-based, dementia-inclusive physical activity that is tailored for people with young onset dementia may be particularly effective in providing support and optimising health outcomes post-diagnosis.