IntroductionIndividuals who access at-risk mental state (ARMS) services often have unusual sensory experiences and levels of distress that lead them to seek help. The Managing Unusual Sensory Experiences (MUSE) treatment is a brief symptom targeted intervention that draws on psychological explanations to help account for unusual experiences. Practitioners use formulation and behavioural experiments to support individuals to make sense of their experiences and enhance coping strategies. The primary objective of this feasibility trial is to resolve key uncertainties before a definitive trial and inform parameters of a future fully powered trial.Methods and analysis88 participants aged 14–35 accepted into ARMS services, experiencing hallucinations/unusual sensory experiences which are considered by the patient to be a key target problem will be recruited from UK National Health Service (NHS) sites and randomised using 1:1 allocation (stratified by site, gender, and age) to either 6–8 sessions of MUSE or time-matched treatment as usual. Participants and therapists will be unblinded, research assessors are blinded. Blinded assessment will occur at baseline, 12 weeks and 20 weeks postrandomisation. Data will be reported in line with Consolidated Standards of Reporting Trials. Primary trial outcomes are feasibility outcomes, primary participant outcomes are functioning and hallucinations. Additional analysis will investigate potential psychological mechanisms and secondary mental well-being outcomes. Trial progression criteria follows signal of efficacy and uses an analytical framework with a traffic-light system to determine viability of a future trial. Subsequent analysis of the NHS England Mental Health Services Data Set 3 years postrandomisation will assess long-term transition to psychosis.Ethics and disseminationThis trial has received Research Ethics Committee approval (Newcastle North Tyneside 1 REC; 23/NE/0032). Participants provide written informed consent; young people provide assent with parental consent. Dissemination will be to ARMS Services, participants, public and patient forums, peer-reviewed publications and conferences.Trial registration numberISRCTN58558617.