Background: Advanced cancer significantly impacts patients' and family carers' quality of life. When patients and carers are supported concurrently as a dyad, the wellbeing of each person is optimised. FOCUS is a dyadic, psychoeducational intervention developed in the USA, shown to improve the wellbeing and Quality of Life (QoL) of patients with advanced cancer and their primary carers. Originally a nurse-delivered in-person intervention, FOCUS has been adapted into a self-administered web-based intervention for European delivery.Objective: To: 1) adapt FOCUS to the Australian context (FOCUSau); 2) evaluate the effectiveness of FOCUSau in improving the emotional wellbeing and self-efficacy of patients with advanced cancer and their primary carer relative to a usual care control group, 3) compare health care utilisation between the intervention and control groups; and 4) assess the acceptability, feasibility and scalability of FOCUSau in order to inform future sustainable implementation of the intervention within the Australian health care system.Methods: FOCUS will be adapted prior to trial commencement, using an iterative stakeholder feedback process to create FOCUSau. To examine the efficacy and cost-effectiveness of FOCUSau and assess the acceptability, feasibility and scalability we will use a pragmatic phase III hybrid effectiveness-implementation trial, with an integrated research design that includes a digital health evaluation. Participants will include patients with cancer who are over 18 years of age; able to access the internet and can identify a primary support person/carer who can be also approached for participation. Sample size: 173 dyads in each arm (i.e. 346 dyads in total). Patient-carer dyad data will be collected at three time points: baseline (T0) completed pre-randomisation, first follow-up (T1) at 12 weeks post-baseline; second follow-up (T2) at 24 weeks post-baseline.Results: Funded March 2022. Recruitment anticipated to commence by March 2024.Conclusions: If shown to be effective, this intervention will improve the wellbeing of patients with advanced cancer and their family carer, regardless of their location or current level of health care support. Clinical Trial: ClinicalTrials.gov on the 13th of