Currently, very few guidelines for supportive care for children with cancer exist. In the Netherlands, nationwide guidelines are over 10 years old and mostly based on expert opinion. Consequently, there is growing support and need for clinical practice guidelines (CPGs), which ought to be developed with a well-defined methodology and include a systematic search of literature, evidence summaries, and a transparent description of the decision process for the final recommendations. Development of CPGs is time consuming; therefore, it is important to prioritize topics for which there is the greatest clinical demand.This study aims to prioritize childhood cancer supportive care topics for development of CPGs.A Delphi survey consisting of two rounds was conducted to prioritize relevant childhood cancer supportive care topics for the development of CPGs. A group of experts comprising 15 pediatric oncologists, 15 pediatric oncology nurses, and 15 general pediatricians involved in care for childhood cancer patients were invited to participate. All relevant supportive care topics in childhood cancer were rated.In both rounds, 36 panellists (82%) responded. Agreement between panellists was very good, with an intraclass correlation coefficient of 0.918 (95% confidence interval (CI) = 0.849-0.966, p < 0.001) in round 2. The ten topics with the highest score in the final round were infection, sepsis, febrile neutropenia, pain, nausea/vomiting, restrictions in daily life and activities, palliative care, procedural sedation, terminal care, and oral mucositis.We successfully used a Delphi survey to prioritize childhood cancer supportive care topics for the development of CPGs. This is a first step towards uniform and evidence-based Dutch guidelines in supportive care in childhood cancer. Even though performed nationally, we believe that this study can also be regarded as an example starting point for international development of CPGs in the field of supportive care in cancer or any other field for that matter.