Haemophilus parainfluenzae, which belongs to the HACEK (Haemophilus ssp, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae) group, is a rare cause of subacute endocarditis and may lead to ischemic stroke. A 65-year-old female patient previously diagnosed with rheumatic valve disease was submitted to surgical mitral valve repair in 1996. Physical examination did not reveal any murmurs; physical examination of the lungs and abdomen was normal. The patient was admitted to hospital with progressive dyspnea, dry cough, and fever. Transesophageal echocardiogram revealed an approximately 8-mm filamentous image with chaotic motion in the ventricular face of the anterior mitral valve leaflet compatible with vegetation. Treatment with ceftriaxone and gentamicin was initiated. Haemophilus parainfluenzae grew in five blood culture samples. Along the hospital stay, the patient's level of consciousness decreased, and she was diagnosed with ischemic stroke of cardioembolic etiology. The patient developed septic shock refractory to the prescribed treatment and died 12 days after admission. Even though the patient started being treated for endocarditis before the infectious agent was identified, the prompt use of antimicrobials hindered the growth of Haemophilus parainfluenzae and made its isolation difficult.