RESUMEN
OBJECTIVE: When children participate in research protocols, consent (by a parent or legal guardian) and assent (by the children) must be given. Understanding research protocols can be challenging for an adult and even more difficult for a child. The aim of this study was to describe the development of a comic book created to facilitate children's understanding of informed assent with clear and simple language. METHODS: Five researchers with scores above seven according to the Fehring criteria developed the comic book, avoiding the use of technical terminology. Twenty children between 7 and 12 years old, and enrolled in a larger study, responded using a Likert scale and questions about the clarity of texts and illustrations. The final version met National Health System Resolutions (Resoluções do Conselho Nacional da Saúde - CNS n° 196/1996 and 466/2012). RESULTS: The comic book assent presents a short story containing information about a real study: the invitation to participate, objectives, methods, instruments, procedures, risks, benefits, and the researchers' contact information. Most of the participants answered that they perceived the content of the text to be "Excellent" (40%) and "Very good" (40%), and the illustrations were perceived as "Excellent" (45%) and "Very good" (55%). CONCLUSION: The construction of a simple and clear model of informed assent is possible, and this model should be used in experiments with children.