Background: Self-management of early warning signs of relapse is critical when it comes to having an impact on the relapse rate and developing methods to successfully handle and manage those signs of relapse. Objective: The purpose of this study was to test the validity and reliability of the adapted management of early warning signs of relapse questionnaire. Methods: Consisted of two main steps: first, adapting and validating, which involved a literature review, a panel of experts, the calculation of the CVI, the Kaiser-Meyer-Olkin (KMO) test, Bartlett’s test of sphericity, and exploratory factor analysis (EFA); and secondly, reliability analysis, using the test-retest method, to assess the questionnaire’s internal consistency (Cronbach’s alpha) and reproducibility (intraclass correlation coefficient—ICC). Results: The results showed that the questionnaire adapted was valid and reliable and can represent each item of the questionnaire for assessing the self-management of early warning signs of relapse. Conclusion: This proves that all 20 items used to assess it are appropriate for assessing the effectiveness of the patients’ and their primary caregivers’ abilities to self-manage early warning signs of relapse​