Mucositis is a common and devastating side effect of chemotherapeutic agents in children undergoing chemotherapy. The prevention and management of mucositis are necessary to improve these children's quality of life. Oral care is a recommended strategy for preventing and managing oral mucositis. Thus, the objective of this study was to identify the relationship between oral care practice and mucositis incidence. A cross-sectional analytical design was used in this study. A total of 34 children from 3 to 12 years of age with acute lymphoblastic leukemia who were in the last cycle of chemotherapy were recruited through a snowball sampling method. The Oral Assessment Guide (OAG) was administered to assess the severity of mucositis. A majority of the participants (51.5%) had mucositis after completing the last cycle of chemotherapy. Furthermore, there was a statistically significant relationship between their oral care practice at home and mucositis incidence. These results show that oral care at home is linked with the incidence and severity of mucositis. Nurses should educate children with leukemia and their parents regarding good oral hygiene practice.