Background: Children and adolescents have the right to participate in decisions concerning their health and express their views, also regarding hospital experiences. Patient-reported experience measures (PREMs) are valuable tools for systematically incorporating patient voices into healthcare systems. New developments have focused on PREMs for children and adolescents, though they are more commonly used in adults. A recent systematic review mapping their use for children and adolescents indicates a growing interest in this area. However, most PREMs are completed by proxy, in this case parents, so they do not necessarily reflect children’s experiences or align with their rights. Innovation is required to support and engage children and adolescents in responding to these types of questionnaires. Methods: Collaborating with children and adolescents (4–17 years), the primary aim of this study is to develop and validate the tool MyHospitalVoice containing digital and developmentally appropriate PREMs. The secondary aim is to document and evaluate the approaches used to involve children and adolescents and to assess the impact of their involvement. Based on the European Organisation for Research and Treatment of Cancer framework, we will divide its development and validation into four phases. First, we will discuss PREM items with children and adolescents, who will select and prioritise what they perceive as most important. Second, we will create items targeting different age groups (4–7, 8–12, and 13–17 years) and design a responsive digital interface with child and youth friendly ways of responding to the questionnaires. Third, we will explore how children and adolescents perceive MyHospitalVoice using cognitive interviewing techniques and other age-appropriate methods. Last, we will pilot test MyHospitalVoice to explore patient experiences and response rates. In each phase, children and adolescents will play an active role. We will involve young adults as peer researchers in the project group to ensure that their perspectives are part of the decision-making process. Discussion: This project will contribute to research on co-creating with children and adolescents and enhance our understanding of their patient experiences. A validated tool like MyHospitalVoice can help improve quality of care by translating the needs and preferences of children and adolescents into clinical practice.