In this case series, we report a 32-year-old male patient with myocardial infarction and 45-year-old female with portal vein thrombosis with splenic infarcts, which were the initial manifestations of polycythaemia vera. The awareness of myeloproliferative disorders as a possible underlying disease—especially in young patients presenting with myocardial infarction and portal venous thrombosis—is crucial for clinical management, as a missed diagnosis can worsen the patients’ further prognosis.