Background: There is an increasing interest in mobile health (mHealth), the use of mobile devices for supporting self-care in persons with heart failure. However, an established theoretical framework to explain, predict, and understand the phenomena of mHealth to support self-care is lacking. Objective: The aim of this study was to deductively test if the situation-specific theory of heart failure self-care could be applied in the context of persons with heart failure using an mHealth system with a tablet computer connected to a weighing scale to support their self-care. We wanted to test whether the 3 phases of the self-care process (ie, self-care maintenance, symptom perception, and self-care management) could be validated in the experiences of persons with heart failure using an mHealth tool. Methods: A qualitative study design was used with semistructured interviews. Data were analyzed deductively using content analysis and coded according to a structured matrix into 1 of the 3 predefined categories: self-care maintenance, symptom perception, or self-care management Results: Seventeen persons with heart failure, with mean age of 75 years, participated. The mHealth system was found to be feasible, influencing adherence and providing support for maintaining self-care as well as influencing both physical and psychological symptom perception. In persons with heart failure, the mHealth tool experience influenced the development and use of skills and fostered independence in self-care management. An interaction with healthcare professionals was sometimes needed in combination with the mHealth tool. Conclusions: The findings confirmed that "the situation-specific theory of heart failure self-care" could be applied in this context.