The use of mobile applications is widespread in patient monitoring or education today. This study aims to describe the design and development process of a mobile app that supports patient self-care after breast cancer surgery. We used the ADDIE model to develop and test the mobile app. ADDIE (Analysis, Design, Development, Implementation, Evaluation) is a systematic approach based on a standard instructional design model for creating training materials. The model consists of five phases, each with its own set of steps. Once the steps within each phase are completed, the model progresses to the next phase, ultimately resulting in a “usable” product. Different team collaborations were established within each phase, and support was obtained from multiple experts during the design process. Thanks to this model, the information that patients need was transformed into a technological product. This article, which explains the stages of the product design process for mobile applications, provides information that may be helpful to researchers working on similar products.