BACKGROUND: The COVID-19 pandemic significantly disrupted primary care and emergency departments globally, including the UK and Australia respectively, affecting services within these settings, such as first contact physiotherapy services (FCPS) for patients with musculoskeletal conditions. This disruption necessitated rapid adaptation to ensure continuity of care. Before this study, comprehensive adaptations across both primary care and emergency departments FCPS had not been documented. Additionally, the specific adaptation processes, strategies used, and experiences of both staff and patients during the COVID-19 pandemic were unclear. Variations in responses between the UK and Australia also remained unknown. Documenting these rapid adaptations and experiences is crucial for future preparedness, as it provides valuable insights to guide FCPS and similar services, preventing future disruptions and promoting continuity of care. Moreover, findings will contribute significant knowledge to the existing literature. AIM: This study explores rapid adaptation of FCPS for patients with musculoskeletal conditions during the COVID-19 pandemic in the UK and Australia. METHODS: This is an ongoing three-phase sequential mixed-methods study. Phase 1 utilises a cross-sectional survey of physiotherapists in FCPS role in the UK and Australia to assess changes in healthcare delivery during the pandemic, as well as levels of readiness and responsiveness, highlighting similarities and differences. Phase 2 employs a case-study approach, including semi-structured interviews and a review of documents produced to direct the management and implementation of proposed changes in FCPS, to further understand the findings from Phase 1. In phase 3, mixed-methods integration facilitates the development of context specific recommendations for the rapid adaptation of FCPS and similar contexts. These recommendations will be presented to experts for feedback and further refinement. DISCUSSION: The mixed-methods research will provide contextually rich account of FCPS rapid adaptation, providing key learnings that could be applied to implement evidence-informed rapid adaptation in FCPS during public health emergencies.