Cerebral venous thrombosis is a rare consequence of lumbar punctures for intrathecal therapy. We report a patient treated for diffuse large B cell lymphoma with cerebral venous thrombosis after intrathecal Methotrexate administration. In this patient, intrathecal treatment was discontinued and he was successfully treated with high-dose low-molecular-weight heparin subcutaneously. Haematologist must be aware about neurological symptoms of cerebral venous thrombosis as a complication of lumbar puncture especially among patients with high coagulopathy state. If neurological symptom occurs, patient should be referred early to neurologist to avoid fatal outcome and neurological deficit.