Background: Leukemia disease is a common cancer and remains a life-threatening malignancy in adolescents, that affects on adolescents over the world physical health, psychological health and social wellbeing. This study aimed to assess quality of life among adolescents with leukemia. Research design: Descriptive research design was used for this study. Setting: This study was conducted at Mansoura Oncology Out-patient Clinics. Sampling: Convenient sample were used in this study, the total sample included 90 adolescent patients. Tools: two tools used in this study. The first tool: A structured interviewing questionnaire which covers the following parts: Part I: Asocio demographic characteristics of adolescent patients. B-medical history of the adolescents' suffering from leukemia. Part II: knowledge of the adolescents' regarding leukemia disease. Part III: Concerned with practices of adolescents' regarding leukemia disease. Second tool: Concerned with adolescent patients Quality of Life Scale regarding leukemia. Results: 56.7% of adolescent patients were males, 47.8 % of adolescent patients had basic education and 54.4% of the studied adolescent patients were from rural area. 64.4 % of the studied adolescent patients with leukemia hadn't teenagers or relatives with leukemia or cancer disease. 54.5% of the studied adolescent patients with leukemia had average total knowledge regarding leukemia. 84.4 % of the studied adolescent patients with leukemia had satisfactory with total reported practices regarding leukemia. 45.6% of the studied adolescent patients with leukemia had moderate total quality of life level. There were a highly statistically significant relations between total knowledge level of adolescent patients with leukemia and their socio demographic characteristics regarding age and level of education. Conclusion: There were statistically positive correlation between total adolescent patients knowledge, their total practices and total quality of life scores related to leukemia disease. Recommendation: Booklets and posters should be available at outpatient clinics to guidance all adolescent patients about leukemia disease and the treatment. ‫ـــ‬ ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬ ‫ــــــــــــــــــــــــــ‬