Given the social burden and high cost of dementia care in Australia, finding evidence-based approaches that improve outcomes, maintain independence, and reduce the impact on clients and families is essential. Similarly, helping professionals who support these individuals are considered at risk of workplace stress, burnout, and other psychological disturbances. This study evaluated the effects of a Montessori-based approach to dementia care in non-residential respite centres. A mixed methods design incorporated a 20-month prospective observational, cohort-controlled study to compare participants from a community-based respite service that implemented a Montessori-based model of care to those from services that provide ‘care as usual’. Linear mixed modelling assessed group differences on a range of variables, including clients' cognitive, behavioural, and emotional functioning, levels of caregiver burden, and burnout, compassion satisfaction, and workplace engagement among respite staff. No significant differences were found between the groups on the rates of change in the clinical and organisational variables over time. Qualitative analysis revealed challenges to the quality and fidelity of the Montessori program related to clients’ engagement in meaningful roles and activities, the modification and progression of those activities, ensuring tasks were self-correcting or error-free, and the use of Montessori-based communication strategies. The analysis also highlighted implementation barriers associated with levels of training and support, one-on-one time with clients, and aspects of organisational culture that conflicted with Montessori methods. These findings reinforce the need for comprehensive pre-implementation workplace change initiatives to ensure organisations are ready to adopt Montessori values and frameworks of care.