A case of a 58-year-old female patient who presented with significant blood eosinophilia and thromboembolic events is described. The patient was eventually diagnosed as suffering from a disseminated malignancy of gastrointestinal origin. Immunohistochemical studies of the tumor are presented. These studies show that tumor cells produce interleukin-3 and -5 and granulocyte macrophage-colony stimulating factor. These cytokines are known to support differentiation, proliferation, and survival of eosinophils. Their secretion is the probable explanation for the appearance of high blood eosinophilia in this patient. To the best of our knowledge, combined blood eosinophilia and thromboembolism as presenting manifestations of a solid tumor have never been reported.