Annually, more than 300,000 new cases of child and adolescent cancer are diagnosed worldwide, according to the International Agency for Research on Cancer. The numbers are no less alarming in Brazil, in which childhood cancer already reaches the second cause of death among children. The subject increasingly demands the implementation of emergency actions for prevention, early diagnosis and treatment, with a joint and multidisciplinary effort. Most cases require chemotherapeutic treatment, which often results in oral mucositis, the most frequently documented side effect in pediatric immunosuppressed pediatric patients. These oral lesions lead to a considerable impact of quality of life during treatment due to dysphagia, dysarthria, odynophagia and malnutrition. In addition, these injuries contribute to a gateway to opportunistic infections, discontinuation of treatment, longer hospital stay, hospital costs, and often lead to death in more severe cases. The Dentist plays a key role in the hospital setting to diagnose, treat and prevent such injuries. One of the treatments consists of low-intensity laser therapy, which has become one of the most recent and promising treatments, reducing the severity and duration of oral mucositis, and preventing future lesions. This study aims to show the effectiveness of laser therapy in reducing the degree and time of remission of pediatric oncology patients by chemotherapy. We will describe a series of cases, with a quantitative approach, in children from 0 to 19 years of age at a referral hospital in the State of Minas Gerais, Brazil, who had a diagnosis of oral mucositis after chemotherapeutic treatment. The group received daily sessions of Laser Therapy and to evaluate the lesions, a daily recording of the lesions was performed, following WHO protocol. Laser therapy has been shown to be effective in reducing the time of remission and severity of oral mucositis in infantojuvenis patients undergoing chemotherapy.