IntroductionIn vivo exposure is the treatment of choice for specific phobia (SP), but this technique presents limitations related to access and acceptability. Augmented reality (AR) offers advantages like maximising strategies such as ‘variability’ (varying stimuli, durations, levels of intensity or the order of the items), control by the therapist, or ‘exposure to multiple contexts’, which can produce positive effects in terms of fear renewal and generalisation of the results. The aim of this study is to test the efficacy of varying the phobic stimuli during treatment with AR: using multiple stimuli (MS) versus a single stimulus (SS) in participants with SP.Methods and analysisParticipants (N=80) with a diagnosis of an SP of cockroaches will be randomised into two conditions: (1) projection-based AR exposure therapy with MS (P-ARET MS); (2) P-ARET with an SS (P-ARET SS). The measures are related to the efficacy results (fear, avoidance and negative thoughts, performance on the behavioural avoidance test (BAT) and preferences). The primary outcome measure is the BAT, and the secondary outcome measures are the BAT through AR, Fear of Cockroaches Questionnaire, Cockroach Phobia Beliefs Questionnaire, Fear and Avoidance Scales Patient’s Improvement Scale, and Beck Depression Inventory Second Edition. Five evaluation moments will be included: preintervention, postintervention, and 1-month, 6-month, and 12-month follow-ups. The treatment will follow the guidelines of the ‘one-session treatment’. Student’s t-tests to compare the two groups on the post-test will be applied. In addition, two-way analysis of variances with repeated measures in one of the two factors (pretest, post-test and follow-ups) will be carried out to compare intragroup differences.Ethics and disseminationThe Universitat Jaume I Ethics Committee (Castellón, Spain) granted approval for the study (CD/64/2019). Dissemination will include publications and presentations at national and international conferences.Trial registration numberNCT04563403.