Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a prothrombotic disorder, which has been described as a rare adverse effect of the adenoviral-vectored coronavirus disease 2019 (COVID-19) vaccines. The diagnosis is confirmed by the detection of anti-platelet factor 4 (PF4) antibodies by enzyme-linked immunosorbent assay (ELISA) or functional assay in individuals with the appropriate clinical history. Here, we report a case of a patient who presented with a severe intracerebral hemorrhage and thrombocytopenia 14 days after receiving the first dose of the Oxford-AstraZeneca COVID-19 vaccine, with negative PF4/heparin antibodies tested with ELISA, but positive heparin-induced platelet activation assay (HIPAA).