Primary angiosarcoma of the spleen is a very rare neoplasm with a poor prognosis. The definitive diagnosis is usually based on the histologic evaluation of the splenectomy specimen. We describe a case of angiosarcoma diagnosed by fine-needle aspiration cytology prior to splenectomy. A 69-year-old white woman presented with heterogeneous lesions in the spleen during a follow-up computed tomographic scan for a history of liposarcoma of the right buttock. A malignant endothelial neoplasm was diagnosed by fine-needle aspiration cytology using immunocytochemistry, and a splenectomy confirmed the presence of angiosarcoma. To our knowledge, this is the first well-documented and confirmed case of primary angiosarcoma of the spleen diagnosed by fine-needle aspiration cytology. This report emphasizes the value of fine-needle aspiration cytology as an important diagnostic tool in splenic neoplasms.