Background <p>Asthma is the most common chronic disease in children, yet adherence to treatment remains poor due to barriers in communication and self-management. Shared decision-making (SDM) can improve adherence, but no decision aid currently exists for paediatric asthma. This gap limits children’s engagement in treatment decisions, highlighting the need for a tailored patient decision aid. The aim was to develop a decision aid to support SDM between children with asthma, their parents, and healthcare providers (HCPs), followed by an evaluation of its acceptability and usability.</p> Methods <p>A user-centred, iterative co-design approach was used, involving children aged 6–18 years with physician-diagnosed asthma, their parents, and healthcare providers (including paediatricians, asthma nurses, and general practitioners). An initial needs assessment identified key challenges in asthma-related decision-making. These insights informed eight structured co-creation sessions focusing on identifying decision points, exploring preferences, and shaping content and format of the decision aid. Usability and acceptability were tested with end-users, and the final version was independently reviewed against the IPDAS checklist by two researchers to assess quality and completeness.</p> Results <p>A needs assessment (<i>n</i> = 37) with HCPs, patients, and caregivers identified substantial information gaps, with many patients and parents unaware of treatment options or potential side effects. HCPs emphasised the potential value of a decision aid in improving information delivery and encouraging SDM. In eight co-creation sessions, a multidisciplinary group (<i>n</i> = 18) collaborated to develop and refine two complementary decision aids. Feedback highlighted improved clarity, age-appropriate design, and relevance for real-life consultations. In the final phases, both decision aids were tested for acceptability and usability, showing high user satisfaction with minor revisions made (<i>n</i> = 32). A quality assessment was conducted by two independent reviewers. Both tools met all 12 IPDAS criteria. These results confirm their quality and suitability for implementation in practice.</p> Conclusion <p>The decision aids were well received by patients, parents and HCPs and met IPDAS criteria. They address critical unmet needs in paediatric asthma care by supporting informed decision-making. These tools have the potential to improve the quality of clinical consultations and promote more patient-centred care in the treatment of childhood asthma.</p> Clinical trial number <p>Not applicable.</p>