OBJECTIVE: The Spanish national health system (SNHS) faces significant barriers to psychological care, such as long waiting lists and a lack of human resources. In addition, with emotional disorders being the most prevalent disorders worldwide, and less than half of those affected receiving proper treatment, there is an urgent need for new treatment alternatives for this group of disorders. The Unified Protocol (UP) is presented as a possible solution that has amply demonstrated its efficacy in different formats and contexts. Another promising alternative involves the use of blended formats, combining face-to-face UP sessions with a UP-based application. This manuscript focuses on the description of RegulEm, a UP-based application developed following a participatory design approach. In addition, a case example of receiving UP in a blended format in a specialized mental health unit of the SNHS is presented. METHODS: The following components of RegulEm are described: content and exercises of the modules; aesthetics and multimedia-based content; intervention delivery; testimonials section; emotional and motivation assessment; exposure hierarchy for guided in vivo and imaginal exposure; emergency button and Gamification. A case example of a 26-year-old male patient with anxiety and depressive symptoms receiving UP in a blended format in a specialized mental health unit of the SNHS is presented. RESULTS: The user showed improvements in emotional regulation skills, anxiety, and depressive symptoms over time, though stressors remained. RegulEm allowed independent progress between face-to-face UP sessions, but low internalization of some content emphasized the importance of therapist guidance in face-to-face sessions. User feedback highlighted satisfaction with the intervention but improvement proposals for RegulEm were identified, such as simplifying emotional exposure exercises. CONCLUSION: This manuscript describes in detail the first UP-based smartphone application's components and illustrates important implications, such as enabling users to progress at their own pace between sessions and advancing more quickly in the intervention.