Multiple caries in a pediatric patient often requires dental treatment under general anesthesia, especially when the patient is suffering from a systemic disease. The patient was a 6-year-old boy with Marfan syndrome and needed extensive dental treatment. Marfan syndrome is an inherited disorder resulting from mutations in Fibrillin-1 gene. Patients are known to have mainly cardiovascular, ocular, and musculoskeletal problems. Although clinical symptoms of the syndrome are age-related, thus hindering early diagnosis of the disease in young children, our patient had been confirmed by a gene study at a younger age. Medical history of the patient revealed moderate to severe mitral regurgitation and aortic root dilatation, which required mitral valve replacement surgery with a mechanical valve. As a result, the patient was taking warfarin post-operatively and changes in medication had to be made before the dental treatment. Also, prophylactic antibiotics had to be given before the treatment for prevention of (to prevent the) infective endocarditis. With careful control of the medications and bleeding tendency, general anesthesia and the treatment were done successfully without any complications.