We present the first documented acute bacterial sinus infection with Staphylococcus schleiferi in a 58-year-old male recovering from endoscopic sinus surgery recovering on postoperative oral corticosteroids. The patient reported, within 1 month of surgery, treating an outer ear infection in his dog that was culture positive for Staphylococcus schleiferi and Corynebacterium sp. and developing an acute exacerbation of his sinus symptoms with increased purulent drainage, facial pain, and increased aural fullness. Nasal endoscopy was notable for purulence and thick mucus in multiple sinuses, which was positive on culture for S. schleiferi. He underwent treatment with trimethoprim/sulfamethoxazole that resolved the active infection. S. schleiferi has shown only rare transmission to a human host in both immunocompetent and immunocompromised patients. Often, this bacterial pathogen will present as a skin infection or outer ear infection in canines and serves as the potential source of infection in humans as they treat their canine companions. This marks the first documented case of acute bacterial sinusitis caused by this bacterial pathogen in the human literature and warrants continued observation as another potential zoonotic pathogen that may cause sinus exacerbations in susceptible populations.