Background: Several studies showed that cancer therapies during tooth development are associated with dental abnormalities, including enamel defects, arrested tooth development, microdontic teeth, and agenesis. Study design: We describe the case of a nine-year-old boy treated for acute myeloid leukemia at 15 months of age, who presents several dental abnormalities resulting from anticancer treatment. Results: The patient was included and treated according to the ELAM 02 French protocol. Six years after allogenic hematopoietic stem cell transplantation, the intraoral and radiographic examination highlighted the agenesis of the second permanent molars and three of the four second premolars, microdontia of the first premolars, root stunting of the central incisors and first premolars, rootlessness of the first permanent molars, and enamel defects localized at the permanent incisors and canines. As a first step to reduce enamel defects, restorations with resin composite (Tetric EvoCeram® A2, Ivoclar Vivadent) were performed under a dental dam. Orthodontic treatment was contraindicated due to arrested tooth development, short roots, and a risk of resorption is considered too important. Conclusion: The young age at diagnosis (<5 years of age) and intensive chemotherapy (especially myeloablative conditioning with high doses of cyclophosphamide and Busulfan) could explain the severity of the dental abnormalities. This case illustrates the importance of systematically scheduling a dental follow-up in parallel with the onco-hematologic follow-up allowing the clinicians to prevent, detect, and propose early intervention for dental late effects.