According to recent Congressional testimony by the Secretary for Veterans Affairs (VA), improving the timeliness of services is one of five current priorities for VA. A comprehensive access measure, grounded in veterans' experience, is essential to support VA's efforts to improve access. In this article, the authors describe the process they used to develop the Perceived Access Inventory (PAI), a veteran-centered measure of perceived access to mental health services. They used a multiphase, mixed-methods approach to develop the PAI. Each phase built on and was informed by preceding phases. In Phase 1, the authors conducted 80 individual, semistructured, qualitative interviews with veterans from 3 geographic regions to elicit the barriers and facilitators they experienced in seeking mental health care. In Phase 2, they generated a preliminary set of 77 PAI items based on Phase 1 qualitative data. In Phase 3, an external expert panel rated the preliminary PAI items in terms of relevance and importance, and provided feedback on format and response options. Thirty-nine PAI items resulted from Phase 3. In Phase 4, veterans gave feedback on the readability and understandability of the PAI items generated in Phase 3. Following completion of these 4 developmental phases, the PAI included 43 items addressing 5 domains: logistics (five items), culture (three items), digital (nine items), systems of care (13 items), and experiences of care (13 items). Future work will evaluate concurrent and predictive validity, test/retest reliability, sensitivity to change, and the need for further item reduction. (PsycINFO Database Record (c) 2020 APA, all rights reserved).