A 49-year-old veterinarian presented with a primary bacteremia of Streptococcus equi subsp. zooepidmicus, pancytopenia, and splenomegaly. Hairy cell leukemia (HCL) was diagnosed and successfully treated with cladribine. Group C streptococci are animal pathogens and rarely cause infections in humans. Comorbidity is often essential for acquiring a severe group C streptococci infection. Granulocytopenia and impaired T cell immunity make hairy cell leukemia patients susceptible for severe infections.