Poor dentition and/or dental infection due to insufficient oral care are presumed to be risk factors for infective endocarditis (IE). We present a case of endocarditis caused by Granulicatella adiacens and Sjögren's syndrome (SS) with oral complications diagnosed simultaneously. A 67-year-old woman was admitted to our hospital with fever, general fatigue, arthralgia, and back pain. She was diagnosed with primary SS according to the criteria of the American-European Consensus Group. Transthoracic echocardiography carried out to examine her persistent fever revealed vegetation formation (14 × 5 mm) on the aortic valve and her blood cultures were positive for G. adiacens. According to modified Duke's criteria, she was also diagnosed with IE. She underwent aortic valve replacement and was administered ampicillin with gentamicin for 6 weeks following surgery. G. adiacens, which is formerly known as one of the nutritionally variant streptococci, is found as part of the normal microbiota of the oral cavity. The patient had chronic periodontitis associated with SS that likely predisposed to G. adiacens bacteremia and subsequent seeding of the aortic valve. Patients with SS may be at risk of IE because of the increased risk of bacteremia from oral complications such as dental caries or periodontal disease. An association between SS and IE has not yet been reported. Our case indicates that SS may be the underlying pathology in patients with IE due to an oral bacterium.