The differential diagnosis of optic neuritis is broad and varied. We report the case of a 24-year-old Brazilian man who presented with five-week history of fever, malaise, myalgia, severe fatigue, tender right preauricular lymphadenopathy, and acute vision blurring associated with right optic disc swelling and exudates in a macular star pattern. His illness developed soon after an infestation of fleas broke out among his cats. Diagnosis of ocular bartonellosis was confirmed by serological and molecular analyses targeting amplification of Bartonella spp. htrA gene. Signs and symptoms only improved after initiation of antimicrobial therapy.