Background: Gemella haemolysans is a gram-positive coccus that colonizes the genitourinary system, gastrointestinal system, and upper respiratory tract as an opportunistic pathogen. Berge et al. found that the frequency of Gemella species bacteremia was 4.5 and infective endocarditis was 0.31 per 1,000,000 inhabitants yearly. We report the first case of G. haemolysans bacteremia presenting as new-onset atrial fibrillation with rapid ventricular response (RVR) and acute respiratory failure and present a case series on G. haemolysans bacteremia and infective endocarditis. Case Presentation: A 58-year-old male with a past medical history including aortic valve bioprosthetic replacement, type 2 diabetes, hypertension, and coronary artery stenting and bypass surgery presented with shortness of breath and confusion. Examination and testing revealed a 40.4°C fever, acute respiratory failure, atrial fibrillation with RVR, congestive heart failure, lactic acidosis, and acute renal failure, with no drug use, dental wounds, or pneumonia. Diltiazem, metoprolol, aspirin, atorvastatin, insulin, heparin, and ceftriaxone were started. TTE and TEE revealed no clear vegetations. Blood cultures revealed Gemella haemolysans. He became stable after 4 days, was electrically cardioverted to sinus rhythm with first-degree AV block, progressed to complete heart block, then had a temporary pacer placed. A repeat TEE demonstrated an aortic root abscess. He underwent redo sternotomy and homograft placement with no complications and was discharged with instructions to complete a six-week course of ceftriaxone. Discussion: Our patient presented with multiple comorbidities at a younger age compared to the mean (66) and median (70) age of the 4 bacteremia cases in our 8-case series. Preemptive antibiotic treatment may be warranted for prosthetic heart valve patients, with the possibility of urgent valve replacement surgery. Several antibiotics were previously reported in case studies with varying results. The shortest course was 16 days, with most courses lasting 4 to 7 weeks. With no standard treatment, this case series suggests G. haemolysans tends to be susceptible to beta-lactam agents. Conclusion: Our case highlights the importance of a multidisciplinary approach in the diagnosis and management of Gemella haemolysans bacteremia, particularly in patients with complex medical histories and prosthetic heart valves.