Due to modern antiretroviral therapy (ART), HIV-positive patients have an almost normal life expectancy. The result is an increase in non-HIV-associated cancers among HIV-infected patients. The effects and side effects of the new checkpoint inhibitors, e.g. anti-PD-1 antibodies (PD1 AK) in HIV-infected patients with an altered immune system have not yet been sufficiently investigated. In the presented case report, a patient with metastatic Merkel cell carcinoma and a newly diagnosed HIV infection was treated with an antiretroviral therapy and pembrolizumab. Therapy with the anti-PD-1 antibody showed a complete remission after 6 months and a rapid improvement of the immune status. Treatment of an HIV-infected patient with PD-1 antibodies appears to be effective and tolerable and does not appear to have a negative effect on the course of the HIV infection. Thus, anti-PD-1 antibodies are a therapeutic option for HIV-positive patients with metastatic Merkel cell carcinoma.