Four types of Kaposi sarcoma (KS) have been described, all of which are caused by human herpesvirus-8 (HHV-8). The incidence of KS in the United States is highest among HIV-positive homosexual men and elderly men of Eastern European, Jewish, or Mediterranean descent. However, few reports describe KS in HIV-negative, immunocompetent heterosexual men in the United States. HHV-8 is transmitted largely via saliva and close sexual contact, whereas there are only a handful of reports of transmission via blood and blood products. We report a case of an HIV-negative, immunocompetent heterosexual man who acquired KS via blood transfusion. A 77-year-old immunocompetent, monogamously heterosexual, HIV-negative Irish man presented with a biopsy-proven KS lesion on the right thigh. Past surgical history included a coronary artery bypass graft, during which he received a blood transfusion from an unknown donor source. His ecchymotic KS lesions progressed while on doxycycline, intralesional vinblastine, and topical anti-angiogenic medications. The patient eventually achieved stabilization of KS lesions with acitretin. Our case report emphasizes the need to characterize the phenotype and transmission route of HHV-8 in heterosexual, immunocompetent patients in geographic regions with low HHV-8 seroprevalence.