Background and Objectives: Haematological malignancies account for approximately 40% of all cancers by the age of 15 years. Acute leukaemia (AL) account for one-third of childhood cancer cases; consisting of Acute Lymphoblastic Leukaemia (ALL) and Acute Myeloid Leukaemia (AML). The aim of this work is to describe the epidemiological, clinical, biological and evolutionary characteristics of children with acute leukaemia in the western and south-western region of Algeria. Patients and Methods: A three-year retrospective study was undergone from January 2016 to December 2018 on children with acute leukaemia. The study was conducted at the paediatric oncology department of the anti-cancer -Emir AEK- of Missreghine in Oran. Results: During this period, we identified 135 cases of diagnosed AL. The sex ratio M/F was 1.1. The “two to five-year” age group was the most affected. The prevalence of ALL, AML, and biphenotypic acute leukaemia (BAL) was 60.45%, 23.88%, and 15.57%, respectively. The clinical signs were mainly presented by the tumour syndrome dominated by the presence of lymphadenopathy (63%) and splenomegaly (56.3%). The most frequent abnormal blood abnormalities were anaemia (66.66% in ALL and 28.14% in AML), thrombocytopenia (75.9% in ALL and 24.4% in AML) and leukocytosis (76.3% ALL and 23.7% AML). Conclusion: Paediatric acute leukaemia is a real public health problem that requires special care and attention. This management must involve all epidemiological, clinical and biological aspects for this highly sensitive age group.