BACKGROUND: Cancer care can negatively impact children's subjective well-being. In this research, well-being refers to patients' self-perception and encompasses their hospital and care delivery assessment. Playful strategies can stimulate treatment compliance and have been used to provide psychosocial support and health education; they can involve gamification, virtual reality, robotics, and healthcare environments. This study aims to identify how playfulness, whenever applicable, can be used as a strategy to improve the subjective well-being of pediatric cancer patients in the Brazilian Unified Health System. METHODS: Sixteen volunteers with experience in pediatric oncology participated in the study. They were physicians, psychologists, child life specialists, and design thinking professionals. They engaged in design thinking workshops to propose playful strategies to improve the well-being of pediatric cancer patients in the Brazilian Unified Health System. Data collection consisted of participatory observations. All activities were video recorded and analyzed through Thematic Analysis. The content generated by the volunteers was classified into two categories: impact of cancer care on children's self-perception and children's perceptions of the hospital and the care delivery. RESULTS: Volunteers developed strategies to help children deal with time at the hospital, hospital structure, and care delivery. Such strategies are not limited to using playfulness as a way of "having fun"; they privilege ludic interfaces, such as toys, to support psychosocial care and health education. They aim to address cancer and develop communication across families and staff in a humanized manner, educate families about the disease, and design children-friendly environments. Volunteers also generated strategies to help children cope with perceptions of death, pain, and their bodies. Such strategies aim to support understanding the meaning of life and death, comprehend pain beyond physicality, help re-signify cancer and children's changing bodies, and give patients active voices during the treatment. CONCLUSIONS: The paper proposes strategies that can improve the well-being of pediatric cancer patients in the Brazilian Unified Health System. Such strategies connect children's experiences as inpatients and outpatients and may inform the implementation of similar projects in other developing countries.