Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders commonly characterized by excessive production of blood cell lineages. The JAK2 V617F mutation plays a crucial role in the pathogenesis of these conditions, often leading to thrombotic complications. Here, we present the case of a 21-year-old man who presented with acute abdominal pain and was found to have portal vein thrombosis with splenomegaly. Imaging studies confirmed chronic portal vein thrombosis with extensive collateral circulation. Laboratory evaluation revealed an elevated platelet count, and genetic testing confirmed the presence of the JAK2 V617F mutation, suggestive of essential thrombocythemia. The patient was managed with anticoagulation (apixaban) and cytoreductive therapy (hydroxyurea). This case emphasizes the importance of considering underlying MPNs in young patients presenting with unusual thrombotic events, and highlights the significance of early diagnosis and targeted treatment in improving patient outcomes.