Background Theoretically, behavioural activation may have a valuable role to play in the treatment of depression among young people with emerging/early psychosis, however we lack trial evidence concerning its acceptability and feasibility. This study will establish the feasibility of clinician-delivered behavioural activation as an adjunct to standard care for this population. We aim to train and support clinicians in delivering behavioural activation to improve depressive symptoms in young people with early/emerging psychosis. Our objectives are to: 1. Establish the number of young people with early/emerging psychosis with clinically meaningful depression symptoms. 2. Establish the proportion of clinicians that complete the behavioural activation training and are deemed to be competent. 3. Determine the proportion of eligible participants approached who agree to consent to the research. 4. Determine the proportion of participants that complete baseline measures, complete behavioural activation treatment (attending for at least fifteen minutes in a minimum of eight sessions), and complete follow-up measures (immediately post-intervention and at 3 months follow-up). 5. Establish clinicians' fidelity to treatment (by recording randomly selected treatment sessions and completing a fidelity checklist). 6. Calculate preliminary efficacy of behavioural activation against primary and secondary outcomes. 7. Explore participants' experiences of facilitating behavioural activation (clinicians) and receiving behavioural activation (young people with emerging/early psychosis). Method This is a pilot controlled clinical trial with a two-arm parallel-group study. Approximately 60 young people with emerging/early psychosis will be randomly allocated to either behavioural activation treatment plus standard care or standard care alone. The primary outcome: depressive symptoms; and secondary outcomes: negative symptoms, overall psychiatric symptoms, medication side effects and functioning, will be assessed at baseline, post-intervention and at 3-months follow-up. The protocol is registered with the Australian New Zealand Clinical Trials Registry (reference number: ACTRN12622000756729). Discussion The findings will inform the design of a full-scale randomised controlled trial.