The presence of rheumatic heart disease (RHD) and systemic lupus erythematosus (SLE) has rarely been described in one patient. This report describes an adolescent Polynesian male with RHD who developed SLE years later. Initially, he fulfilled modified Jones criteria for rheumatic fever with aortic insufficiency, transient arthritis, elevated streptococcal titers, and a high erythrocyte sedimentation rate with a negative antinuclear antibody (ANA). He responded well to nonsteroidal anti-inflammatory and penicillin prophylaxis, which supported the diagnosis of rheumatic fever. Five years after his RHD diagnosis, he developed pancreatitis with glomerulonephritis, nephrosis, and pancytopenia. In addition, laboratory results revealed that he had multiple autoantibodies: anti-Sm and extremely elevated anti-dsDNA and ANA, fulfilling diagnostic criteria for SLE. The patient was treated, and he responded to pulse steroids followed by oral steroid therapy. To our knowledge, there are no known reported cases of a patient who was diagnosed with both RHD and SLE and met the clinical criteria for both diseases. The rarity of this concurrent disease process in one patient suggests a possible overlap in humoral immunity toward self-antigens as well as ethnic variability that increases predisposition to rheumatologic diseases.