Certain chemotherapy agents, radiation, and surgery can all negatively impact future fertility. Consults regarding treatment-related risk for infertility and gonadal late effects of these agents should occur at the time of diagnosis as well as during survivorship. Counseling on fertility risk has traditionally varied significantly across providers and institutions. We aim to provide a guide to standardize the assignment of gonadotoxic risk, which can be used in counseling patients both at the time of diagnosis and in survivorship. Gonadotoxic therapies were abstracted from 26 frontline Childrens Oncology Group (COG) phase III protocols for leukemia/lymphoma, in use from 2000-2022. A stratification system based on gonadotoxic therapies, sex, and pubertal status was used to assign treatments into minimal, significant, and high level of increased risk for gonadal dysfunction/infertility. Risk levels were assigned to protocols and different treatment arms to aid oncologists and survivor care providers in counseling patients regarding treatment-related gonadotoxicity. Males were most commonly at high risk, with at least one high-risk arm in 14/26 protocols (54%), followed by pubertal females (23% of protocols) and prepubertal females (15% of protocols). All patients who received direct gonadal radiation or hematopoietic stem cell transplant (HSCT) were considered at high risk. Partnering with patients and their oncology/survivorship team is imperative for effective fertility counseling both prior to and post treatment, and this comprehensive guide can be used as a tool to standardize and improve reproductive health counseling in patients undergoing COG-based leukemia/lymphoma care.