Background: The identification of moderators of exposure-based cognitive behavior therapy (EXCBT) outcome has the potential to: (1) guide the judicious application of the limited resource of EXCBT, and/or (2) identify additional treatment targets for ameliorating the deleterious effects of an identified moderator, thereby enhancing clinical response. Experimental and clinical studies have provided intriguing findings for the moderating influence of positive affect on EXCBT outcomes. Mixed findings for state positive affect (at the time of extinction/exposure trials) as a predictor of EXCBT outcomes stand in contrast to evidence that baseline levels of trait positive affect may be a more effective predictor. As such, questions remain about the best way to assess positive affect as a potential treatment moderator. Objective: This study was designed to investigate: (1) the relative value of state and trait positive affect for predicting the outcome of a single-session virtual-reality exposure intervention for public speaking anxiety in adults attending college, and (2) the role of three related constructs—optimism, hopefulness, and mental health self-efficacy—that may explain the predictive significance of trait positive affect. Methods: State affect is manipulated at an experimental level with affect induction procedures; trait positive affect is measured at baseline. Three dependent measures–a primary outcome of public speaking anxiety and secondary outcomes of social phobia and self-reported valence--are examined. This study relies on a team science approach and is conducted across 12 collaborating sites through the Exposure Therapy Consortium, allowing for replication of all findings across diverse study sites across the world. Results: Data collection for the current study began in October 2024 and is projected to end by August 2025. We expect to complete data analysis and submit results for publication in approximately October 2025. Conclusions: The current study will help to clarify the relationship between positive affect (state and trait), exposure learning, and three related constructs (optimism, hopefulness, mental health self-efficacy). These findings will illuminate strategies for future treatment improvement and enhanced efficacy. Clinical Trial: ClinicalTrials.gov Identifier NCT06593847; https://clinicaltrials.gov/study/NCT06593847