In subacute endocarditis caused by Staphylococcus viridans, the bacteria typically damages the heart by forming vegetations on heart valves. These vegetations consist of bacteria, platelets, and fibrin, leading to inflammation and potential valve dysfunction.Endocarditis, an infection of the heart's inner lining, can be serious, affecting valve integrity and possibly causing systemic complications. The severity varies, but complications may include heart failure, embolism, or abscess formation. This case report details a 28-year-old male patient diagnosed with subacute endocarditis caused by Staphylococcus viridans. The infection resulted in the formation of vegetations on heart valves, prompting surgical intervention. The patient underwent aortic valve replacement (AVR) with a mechanical heart valve. The abstract explores the clinical implications and management strategies for subacute endocarditis caused by Staphylococcus viridans, shedding light on the challenges and outcomes associated with this condition.