In mild asthma, as-needed budesonide-formoterol offers similar protection from severe exacerbations as daily inhaled corticosteroids (ICS), with lower ICS exposure but slightly increased symptoms. We sought to develop an electronic decision aid to guide discussions about the pros and cons of these first-line options, while identifying and integrating user preferences. Methods: Following International Patient Decision Aid Standards, we created a mild asthma decision aid prototype comparing convenience, clinical outcomes, cumulative ICS dose exposure, costs, and side-effects of each option. After face validation, the prototype was iteratively adapted through rapid-cycle development. Each cycle consisted of a patient focus group and a primary care physician interview. We made user preference-based improvements after each round, until reaching a pre-set stopping criterion (no new critical issues identified). We then performed a summative qualitative content analysis. Results: Over 5 cycles, we recruited 21 asthma patients (12/21 women, 10/21 ≥ 60 years old) and 5 physicians. Serial changes included simplification and reduction of text and reading level, inclusion of an ICS "myths" section and elaboration of patient-friendly infographics for numerical comparisons. User preferences fell within Content, Format, and tool use Process themes. In response to decision-making preferences, we created a complementary one-page conversation aid for patient-provider use at the point-of-care. Conclusions: We present preference-based electronic patient decision and conversation aids for treatment of mild asthma. Our user preference analyses offer useful insights for development of such tools in other chronic diseases. These tools now require integration into point-of-care workflows for measurement of real-world uptake and impact.