Introduction <p>Anxiety disorders are associated with a high disease burden throughout the life span. Anxiety disorders in older adults, however, remain frequently untreated, and when treated, pharmacotherapy predominates despite age-related risks and a preference for psychotherapy. Exposure Therapy is the most effective intervention for anxiety disorders and is a suitable treatment method to be delivered in primary care centres by mental health nurses. The primary objective of this study is to evaluate the (cost-) effectiveness of ET delivered by trained MHNs compared to usual care in reducing anxiety symptoms and improving quality of life among older adults with anxiety disorders in primary care. The secondary objective is to examine secondary outcomes, including comorbid depressive symptoms and disorder-specific anxiety symptoms. We also aim to investigate potential predictors and moderators of treatment outcome, as well as possible mechanisms of change in exposure therapy for older adults with anxiety disorders.</p> Methods <p>A multi-centre cluster-randomised controlled trial conducted in primary care with two parallel groups: (a) exposure therapy, and (b) usual care, with one-year follow-up. Participants must meet the criteria for a primary Diagnostics and Statistical Manual of Mental Disorders, fifth edition anxiety disorder. Exclusion criteria are earlier treatment for anxiety disorder, other somatic and/or psychiatric morbidity that could interfere with diagnostics or treatment, being terminally ill, and having a moderate to severe cognitive impairment and stable pharmacotherapy use. The intervention consists of eight 30-min ET sessions delivered over 12 weeks. Primary outcome measures are anxiety severity as assessed with the Geriatric Anxiety Inventory, societal costs as assessed with the Trimbos and iMTA questionnaire on Costs associated with Psychiatric illness, and quality of life using the EuroQol 5 Dimension 5 Level version.</p> Discussion <p>Even though participating in present study involves a time investment for patients, we expect that they will benefit from the offered exposure therapy in a more effective way than usual care, as we anticipate a beneficial impact on their anxiety symptoms. If proven effective, exposure therapy could represent a valuable addition to existing clinical guidelines for the treatment of anxiety disorders in older adults within primary care settings.</p> Trial registration <p>This study is registered at ClinicalTrials.gov (NCT06770517) on 26 February 2025.</p>