Acute lymphoblastic leukemia is the most common malignancy in children. In children, venous thromboembolism is relatively common. In most cases, venous thromboembolism manifests in patients who are diagnosed with acute lymphoblastic leukemia. Several risk factors associated with acute lymphoblastic leukemia predispose patients to the development of venous thromboembolism. Unlike most reported cases of venous thromboembolism, herein we report a child who developed cerebral venous sinus thrombosis prior to the diagnosis of acute lymphoblastic leukemia. The patient recovered from an attack of acute gastroenteritis with sepsis, pancytopenia, and disseminated intravascular coagulation 2 weeks before the development of thrombosis. Her laboratory workup for coagulopathy and disseminated intravascular coagulation was normal at the time of diagnosis of cerebral sinus thrombosis. The genetic workup for thrombophilia risk identified several genetic thrombophilia mutations: the homozygous factor XIII V34L and MTHFR A1298C mutations and heterozygous factor V Leiden mutation. Three weeks later, the patient was diagnosed with acute lymphoblastic leukemia. However, it remains questionable whether the thrombotic event was caused by the previous infection of gastroenteritis, sepsis, and disseminated intravascular coagulation picture (which was augmented by her genetic thrombophilia risk), or was it caused by acute lymphoblastic leukemia (that was not detected at early stages with its associated hypercoagulable state), or was it caused by a type of paraneoplastic syndrome. A multifactorial etiology is proposed.