Background: Hypertension (HTN) is a global public health issue. Self-care is an essential component of HTN treatment, but no instruments are available with which to measure self-care of HTN. Objectives: The purpose of this study is to test the psychometric properties of the Self-care of Hypertension Inventory (SC-HI). Methods: Using the Self-care of Chronic Illness theory, we developed a 24-item measure of maintenance, monitoring, and management appropriate for persons with chronic HTN, tested it for content validity, and then tested it in a convenience sample of 193 adults. Exploratory factor analysis was used to identify measure structure. Cronbach's α and factor determinacy scores and were used to assess reliability. Validity was tested with the Medical Outcomes Study General Adherence Scale and the Decision Making Competency Inventory. Results: Seventy percent of the sample was female; mean age was 56.4 ± 13 years; mean duration of HTN was 11 ± 9 years. Removal of 1 item on alcohol consumption resulted in a unidimensional self-care maintenance factor with acceptable structure and internal consistency (α = .83). A multidimensional self-care management factor included “consultative” and “autonomous” factors (factor determinacy score = 0.75). A unidimensional confidence factor captured confidence in and persistence with each aspect of self-care (α = .83). All the self-care dimensions in the final 23-item instrument were associated with treatment adherence and several with decision making. Conclusion: These findings support the conceptual basis of self-care in patients with HTN as a process of maintenance, monitoring, and management. The SC-HI confidence scale is promising as a measure of self-efficacy in self-care.