Serious thromboembolic events with concurrent thrombocytopenia, sometimes accompanied by bleeding, have occurred very rarely following administration of the ChAdOx1 nCoV-19 vaccine. We report the case of a 59-year-old male with an unremarkable medical history who presented to the emergency department with increasing breathlessness five days after receiving the first dose of ChAdOx1 nCov-19. The patient's blood results showed mild thrombocytopenia and a very high D-dimer, and a pulmonary embolism was confirmed through a CT pulmonary angiogram, which led to a provisional diagnosis of vaccine-induced immune thrombotic thrombocytopenia. The condition was then treated with immunoglobulin and intravenous argatroban in line with the guidance from the Expert Haematology Panel focussed on Vaccine-induced Thrombosis and Thrombocytopenia before conversion to apixaban.