Background Patients with leukemia cancer are at risk of developing mucositis that may cause impair quality of life and can not only cause strong pain, but also lead to problems with basic physiological needs as eating and swallowing. Aim: Identify risk factors of oral mucositis among patients with acute leukemia. Design: A descriptive research design was performed in present study. Setting: The study was conducted in the critical care unit, south Egypt cancer institute at Assiut University hospitals. Sample: All available patients with acute leukemia for six month Tool: Assessment personal and medical data of studied groups, mucositis risk factors and oral mucositis assessment scale (OMAS) were used to collect data in this Results: It was found that the most common risk factors in mucositic group were poor oral hygiene, lack of ability of self-oral care, malnutrition (87.9%,78.8%,78.8%) , respectively. While the most common risk factors in non mucositis group were high dose of chemotherapy, poor oral hygiene, lack of ability of self-oral care and Pre-existing dental diseases (70.4%,55.6%,51.9%), respectively. Conclusion: There was statistically significant difference between dehydration, malnutrition, poor oral hygiene and deficit in ability of self-oral care and mucostis occurrence. Recommendations: The nurse must be aware of risk factors that increase prevalence of oral mucositis, develop and implement of oral care guidelines by nurses for mucositic patient with acute leukemia and nurses in intensive care unit should receive training on assessing oral health and identify of risk factors of oral mucositis .