Aim: To report the development of a core set of outcome domains for clinical research involving adults with incontinence-associated dermatitis or at risk, independently from any geographical location or skin colour. Background: The management of incontinence-associated dermatitis is important in caring for incontinent patients. The lack of comparability of clinical trial outcomes is a major challenge in the field of evidence-based incontinence-associated dermatitis prevention and treatment. Core outcome sets may therefore be helpful to improve the value of clinical incontinence-associated dermatitis research. Design: Systematic literature review, patient interviews and consensus study using Delphi procedure. Methods: A list of outcome domains was generated through a systematic literature review (no date restrictions—April 2016), consultation of an international steering committee and three patient interviews. The project team reviewed and refined the outcome domains prior to starting a three-round Delphi procedure conducted between April–September 2017. The panellists, including healthcare providers, researchers and industry were invited to rate the importance of the outcome domains. Results: We extracted 1,852 outcomes from 244 articles. Experts proposed 56 and patients 32 outcome domains. After refinement, 57 panellists from 17 countries rated a list of 58 outcome domains. The final list of outcome domains includes erythema, erosion, maceration, IAD-related pain and patient satisfaction. Conclusion: Erythema, erosion, maceration, incontinence-associated dermatitis -related pain and patient satisfaction are the most important outcome domains to be measured in incontinence-associated dermatitis trials. Based on this international consensus on what to measure, the question of how to measure these domains now requires consideration. Registration: This project has been registered in the Core Outcome Measures in Effectiveness Trials (COMET Initiative) database and is part of the Cochrane Skin Group—Core Outcomes Set Initiative (CSG-COUSIN).