Background: Sleep disorders are common and costly to society. Guidelines from the American Academy of Sleep Medicine (AASM) and the Australasian Sleep Association (ASA) recommend Cognitive Behaviour Therapy for Insomnia (CBTi) as the best treatment modality for insomnia disorder in the long term, however, access issues due to medical first referral pathways and psychology workforce shortages in the community result in increased wait times, reduces efficient care for patients, and adds burden to specialist medical services. Method: This single-site, multiphase, mixed methods study will implement and evaluate a service model of care re-design incorporating a new Direct to Psychology referral pathway for insomnia presentations and a Stepped Care treatment approach including digital intervention in a quaternary public multidisciplinary sleep service. The RE-AIM framework and Standards for intervention Reporting Implementation Studies (StaRI) will be used to guide the development, implementation, evaluation and reporting of this service change. Quantitative data measuring outcomes of the new models of care on key indices of patient clinical outcomes, patient/clinician service satisfaction, and service efficiencies will be collected pre- and post-service change. Discussion: The overarching aim of this project is implement and evaluate a model of care change to the service model in a public tertiary hospital multidisciplinary sleep service. The new Direct to Psychology Stepped Care Model incorporates a Direct to Psychology Insomnia referral pathway along with a Stepped Care approach to treatment, flexibly delivered across the continuum of care. The project will measure the impact of the service change in our target population. The new model of care will be compared to the old service model for key outcomes. We anticipate that the new Model of Care will be acceptable to stakeholders, will produce non-inferior patient outcomes and experience, and will improve patient flow and service efficiency. Trial sponsor: Psychology Department, The Prince Charles Hospital, Rode Rd, Chermside, QLD, Australia, 4032. The sponsor had no role in the study design; data collection, management, analysis, or interpretation; writing of this or future reports; the decision to submit for publication; or ultimate authority over any of these activities. Trial registration: The Protocol was registered on 5/08/2022 with the Australian and New Zealand Clinical Trials Registry (ACTRN12622001086752). The study was conducted in accordance with the protocol version 4: 12 March 2024.