PURPOSE: Symptom tracking systems are essential for identifying symptoms in patients, prompting timely clinical intervention to reduce suffering and improve outcomes for children with cancer. Electronic patient-reported outcome tools have been designed to assess the presence and severity of symptoms and notify clinicians of the patient's condition, facilitating quick and effective symptom management. Utilizing co-design methods allows end user input in the tool development process. This manuscript describes how we used a co-design process to develop an electronic system for tracking the symptoms of children with cancer and their caregivers. METHODS: Collaborative co-design sessions were conducted using a Future Workshop format. Participants were six children with cancer and seven caregivers. Co-design activities were used to gather insights into current symptom reporting practices and to envision an ideal system. Data from these sessions were analyzed using Braun and Clark's method for descriptive thematic analysis. RESULTS: Key themes identified during data analysis included the importance of relationships and interactions with the health care team, miscommunication in symptom reporting, and the need for centralized information storage and timely clinician response. Children in particular indicated challenges with finding the words to share how they are feeling, while caregivers expressed constant worry and the burden of advocating on their child's behalf. CONCLUSIONS: Co-design is a powerful method for envisioning solutions to clinical problems. By involving end users in key stages of the creative process, it is possible to develop solutions that better address underlying challenges and are more enticing for users to adopt. In this study, we successfully used co-design to identify key features for an electronic system intended to improve symptom tracking, facilitate communication with clinicians, and allow for better symptom management. Barriers to consistent electronic system use were also identified, emphasizing the need for simplicity in system design, an engaging interface, and a clear benefit for users.