L-Asparaginase (L-Asp) therapy for pediatric acute lymphoblastic leukemia often results in coagulopathy. In this report, we describe two cases of first remission during reinduction therapy and one onset case during induction therapy in all cases without coagulopathy. We evaluated the comprehensive functions of coagulation and fibrinolysis by simultaneous thrombin and plasmin generation assay (T/P-GA). The ratios of endogenous potential of thrombin (T-EP) and plasmin peak height (P-peak) of patients’ plasmas to those of normal plasma were calculated. All patients showed increased T-EP ratios and decreased P-peak ratios. The most significant difference in both ratios of 1.5–2.6-fold was shown at the later phase of L-Asp therapy, consistent with the lowest levels of fibrinogen (59–106 mg/dL). The patients’ hemostatic dynamics indicate a thrombotic tendency, since their coagulation state was procoagulant and low fibrinolytic. We will study more cases to elucidate the pathologic condition of coagulopathy associated with L-Asp therapy.