Background: The gold standard for symptom reporting in healthcare is self-reporting. Verbal self-reporting is often difficult for children. Children may be more able to accurately and confidently report their symptoms using an mHealth device. The Color Me Healthy app has been developed to facilitate self-reporting in children with cancer. Purpose: The purpose of this project was to evaluate the usability of the revised Color Me Healthy app from the perspectives of children and their parents. Methods: This User Centered Design study was guided by the Technology Acceptance Model with attention to Ease of Use and Perceived Usefulness. Children (6-12 years of age) receiving cancer treatment and their parents were invited to participate in usability evaluations in which they were guided through the app and asked to complete specific tasks within the app. Children and parents participated in brief interviews, and parents also completed the Technology Acceptance Model Perceived Usefulness Scale (TAM PUS). As 5 dyads completed usability evaluations, data were summarized and shared with the developer team to guide additional refinements. Results: Fourteen racially, ethnically, and geographically diverse parent-child dyads participated. After 3 cycles of usability evaluations, children and parents were able to complete key tasks independently, supporting its ease of use. Children and parents also indicated their preference for using the app as a method of symptom reporting, supporting its perceived usefulness. TAM PUS scores also provided evidence that parents deemed the app useful to understand and respond to their child's symptoms. Discussion: mHealth devices, the Color Me Healthy app in particular, are promising methods of symptom self-reporting in children with cancer. The revised version of the Color Me Healthy app demonstrates ease of use and perceived usefulness. Future directions include evaluation of the clinical utility of the revised app in a future study.