Introduction: Oral mucositis corresponds to the most prevalente complication in children with acute lymphoblastic leukemia resulting from oncologic therapy. This condition can cause sepsis, dysphagia and phonetic difficulties. Objective: To evaluate the importance of methods of prevention, diagnosis and treatment of oral mucositis lesions in children with acute lymphoblastic leukemia. Methods: Bibliographic research on PubMed database with keywords: oral mucositis, chemotherapy, oral health, prevention, pediatric patients, isolated, and combinated boolean marker "AND". The articles selection was made through the stipulation of inclusion and exclusion factors, highlighting the temporal limit, language and type of scientific article: Meta-Analysis; Randomized Controlled Trial; Review; Systematic Review. Results: In the diagnosis of oral mucositis the attention care should be directed to clinical aspect of the lesions as well as to the manifested signs/symptoms. It is important to understand the chronological relationship between the appearance of these conditions and the cancer treatment phase, so that it's possible to act preventively in order to avoid more invasive therapies. In the treatment of lesions at an early stage, analgesics, mouthwash solutions, mucosal lining agents and parenteral nutrition may be administered. Conclusion: The success for the maintenance of a healthy oral cavity during oncology therapy lies in the execution of an early diagnosis and the application of adequate preventive/therapeutic measures in each phase of mucositis/cancer treatment. Clinical Implications: In monitoring the cancer patient, it is fundamental intervention of a multidisciplinar team aiming to minimize impact of cancer treatment on oral and general health, and quality of life of child. Palabras clave: Oral mucositis, chemotherapy, oral health, prevention and pediatric patients