BACKGROUND Multiple vaccines have been developed against COVID-19 as a collaborative worldwide effort. On March 18, 2021 the European Medicines Agency reported a serious and rare adverse effect of thrombosis with thrombocytopenia syndrome (TTS) after receiving the ChAdOx1 nCoV-19 vaccine; most of these cases were associated with cerebral venous sinus thrombosis (CVST). To date, there are no cases of TTS-related CVST reported after receipt of either of the 2 mRNA COVID-19 vaccines authorized for use in the United States. We report a case of CVST with the Moderna mRNA vaccine. CASE REPORT A healthy 45-year-old male patient without any risk factors presented with new-onset seizures 8 days after the receipt of the 2nd dose of Moderna (mRNA-1273), with concomitant SAH as a complication. One day prior to admission, he noted headaches and neck pain unrelieved by over-the-counter analgesics. Computed tomography (CT) scan brain without contrast revealed a left frontal lobe intracerebral hemorrhage (ICH) along with subarachnoid hemorrhage (SAH). A subsequent contrast-enhanced magnetic resonance imaging (MRI) brain confirmed the CT findings as well as anterior superior sagittal sinus thrombosis. He had normal platelet count with a negative thrombophilia work-up and cancer screening. He was successfully anticoagulated with heparin and discharged on warfarin without neurological sequelae or further seizures. The case was reported to the US Vaccine Surveillance System. CONCLUSIONS mRNA vaccine-related CVST is an extremely rare phenomenon. More data are needed to establish causality and understand the role of vaccine-related immune response resulting in thrombotic events with or without TTS.