Patients who present with symptoms suggestive of thrombosis 4–42 days after ChAdOx1 nCov‐19 (AstraZeneca) vaccination require urgent blood tests looking for thrombocytopenia, markedly elevated D‐dimer levels, and hypofibrinogenemia. Radiological investigation should be expedited to look for thrombosis. When the diagnosis of vaccine‐induced immune thrombotic thrombocytopenia (VITT) is probable, treatment should be initiated urgently with intravenous immunoglobulin and non‐heparin anticoagulation. Platelet transfusions should be avoided. VITT is a distinct syndrome that is separate from heparin‐induced thrombocytopenia. Standard heparin‐induced thrombocytopenia diagnostic pathways are not appropriate for the diagnostic work‐up, and specific VITT tests are required. For all suspected cases, samples (four citrate and four serum) should be collected before treatment. See the VITT blood test request form at https://www.thanz.org.au/documents/item/579. Readers are strongly encouraged to access the latest updated guidelines available online at https://www.thanz.org.au/documents/item/591. 7