Background: Angiosarcoma (AS) is a rare malignancy originating from lymphatic or vascular endothelial cells. Prognosis of the disease is usually dismal and there is no effective treatment. Immunotherapy has been proved to be effective for various cancer types. Programmed death-ligand 1 (PD-L1) expression is generally recognized as a biomarker for the prediction of response to anti-PD-(L)1 immunotherapies. Methods & results: Here, we discuss a single case by highlighting the treatment of the antiprogrammed cell death protein 1 drug pembrolizumab with high PD-L1 expression. CT scan demonstrated a confirmed size reduction of some lesions compared with original lesions, which indicates the possible clinical benefit. Conclusion: We speculate that early anti-PD-1 treatment may be a promising strategy for angiosarcoma patients with high PD-L1 expression.