Young children with cancer are treated with interventions that can have a high risk of compromising their reproductive potential. ‘Fertility preservation’ for children who have not yet reached puberty involves surgically removing and cryopreserving reproductive tissue prior to treatment in the expectation that strategies for the use of this tissue will be developed in the future. Fertility preservation for prepubertal children is ethically complex because the techniques largely lack proven efficacy for this age group. There is professional difference of opinion about whether it is ethical to offer such ‘experimental’ procedures. The question addressed in this paper is: when, if ever, is it ethically justifiable to offer fertility preservation surgery to prepubertal children? We present the ethical concerns about prepubertal fertility preservation, drawing both on existing literature and our experience discussing this issue with clinicians in clinical ethics case consultations. We argue that offering the procedure is ethically justifiable in certain circumstances. For many children, the balance of benefits and burdens is such that the procedure is ethically permissible but not ethically required; when the procedure is medically safe, it is the parents’ decision to make, with appropriate information and guidance from the treating clinicians. We suggest that clinical ethics support processes are necessary to assist clinicians to engage with the ethical complexity of prepubertal fertility preservation and describe the framework that has been integrated into the pathway of care for patients and families attending the Royal Children’s Hospital in Melbourne, Australia.