BACKGROUND : L-asparaginase is chemotherapeutic agent commonly used in treatment of Acute Lymphoblastic Leukemia. Thromboembolic and to a lesser extent bleeding events are serious complications associated with administration of this drug during the induction phase in ALL especially in children resulting from reduced synthesis of proteins such as Antithrombin & fibrinogen. OBJECTIVE : Evaluation of the coagulopathic side effect of L-asparaginase during the induction phase in treatment of ALL in children by measuring fibrinogen levels before & after administration of this drug. METHODS : An interventional prospective study was performed on 30 newly diagnosed children with ALL, all of them received 9 cycles of L-asparaginase during the induction phase according to UKALL 2003 Protocol. Fibrinogen was measured before & after treatment with L-asparaginase and the results are compared to a control group of 30 healthy children age & sex matched. RESULTS : Reduced fibrinogen level is observed in 13 out of 30 patients (43.3%) after treatment with L-asparaginase ranging from 25 to 110 mg/dl with means fibrinogen before & after treatment of 252 ± 16.40 mg/dl & 158.97 ± 17.88 mg/dl respectively (p < .0001). CONCLUSIONS : Significant reduction in fibrinogen level occurred in childhood ALL patients after treatment with L-asparaginase.