Background <p>Occupation-Based Practice (OBP) is fundamental to occupational therapy, enhancing consumer engagement and outcomes, yet implementation is challenging due to local environments and dominance of impairment-based interventions.</p> Aim <p>To investigate implementation of a service-wide OBP strategy in a large metropolitan tertiary health service over 6&#xa0;years; understand its influence on occupational therapists; identify barriers and facilitators; and observe changes in clinician perceptions supporting sustainability.</p> Methods <p>Qualitative case study at two time points. Participants were occupational therapists and allied health assistants (<i>n</i> = 95 in 2017; <i>n</i> = 39 in 2023). Data was collected through focus groups (<i>n</i> = 8 in 2017; <i>n</i> = 3 in 2023) and multiple documents. Descriptive thematic analysis identified themes and sub-themes.</p> Results <p>Strategic leadership cultivated an OBP culture. Barriers included resource limitations and systemic pressures; facilitators included interdisciplinary support and professional development. Over time, perceptions shifted from conceptual understanding to practical application as OBP became integrated into service culture.</p> Conclusion <p>A service-wide OBP strategy was effectively used in practice. Implementation depended on consistent application, a supportive service culture, and responsive systems. Although COVID-19 negatively impacted OBP, commitment to the strategy supported re-establishment, demonstrating sustainability.</p> Significance <p>A service-wide OBP strategy increases OBP and can be sustained in a tertiary healthcare setting.</p>