Background The capacity for self‐care and positive mental health (PMH) has an influence on well‐being and on one’s approach to chronic illness. Purpose The aim was to determine the level of PMH and self‐care agency as well as the relations among sociodemographic variables, PMH, and the level of self‐care among patients with chronic physical health problems. We also examined correlations between PMH and self‐care agency. Methods A descriptive, cross‐sectional correlational study was conducted with a sample of 209 patients at a primary care center. The instruments used were the Positive Mental Health Questionnaire and the Appraisal of Self‐Care Agency scale. The STROBE statement was used. Results Significant differences were found in the PMH factors in relation to sociodemographic variables and health conditions. Suffering one or more chronic diseases was associated negatively, and significantly, with the capacity for self‐care. The four most prevalent chronic health problems in the sample were hypertension, hypercholesterolemia, obesity, and diabetes mellitus. Linking Evidence to Action In people with chronic physical health problems, there is a positive relationship between PMH and self‐care capacity. An increase in the possibility of caring for oneself saw an increase in PMH; conversely, an increase in PMH brought with it an increased capacity for self‐care as well. Therefore, if actions are taken to increase PMH, the capacity for self‐care will also increase.