INTRODUCTION: Cerebral venous sinus thrombosis (CVST) with cerebral hemorrhage is relatively rare but may result in a catastrophic outcome. Antithrombin III deficiency is an inherited disease that contributes to an increase in the occurrence of thromboembolic events during pregnancy. CASE PRESENTATION: A nulliparous, 34-year-old Chinese lady at 9 weeksâ€™ gestation with underlying antithrombin III deficiency and on treatment dose of low molecular weight heparin. She presented with frontal headache and projectile vomiting. A plain computed tomography (CT) scan and magnetic resonance angiography and venography (MRAV) of brain showed features suggestive of CVST involving superior sagittal sinus with venous infarct and right frontal and left parietal intraparenchymal hemorrhage. Subsequently, she experienced episodes of fainting and loss of consciousness. A repeated brain CT scan showed worsening intraparenchymal hemorrhages with midline shift, subfalcine herniation, and cerebral edema. Therefore, an emergency bilateral craniectomy was performed to relieve the intracranial pressure. Despite the surgery and supportive measures, the patient succumbed to death. CONCLUSION: Due to the highly hypercoagulable state of pregnancy with concomitant antithrombin III deficiency, preconception counselling including optimization of anticoagulant dosage is crucial. In addition, administration of antithrombin III concentrate should be considered during pregnancy for women with antithrombin deficiency.