The purpose of this study was to evaluate the periodontal status and the presence and concentration of Porphyromonas gingivalis (P. gingivalis) and immunoglobulin G (IgG) subclass against P. gingivalis in juvenile idiopathic arthritis (JIA) and its association with rheumatic clinical activity parameters.Rheumatologic conditions and periodontal status were clinically assessed in 51 patients with JIA. P. gingivalis, IgG1 and IgG2, high-sensitivity C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPAs), and human leukocyte antigen B27 were also evaluated.Periodontitis was observed in 21.5 percent of the patients, 23.5 percent of whom were positive for P. gingivalis, which was associated with enthesitis-related arthritis (P<0.035). IgG1 against P gingivalis was associated with RF autoantibodies (P=0.05), and all patients positive for ACPAs had higher anti-P gingivalis IgG1 levels. A significant correlation was found between the presence of limited joint mobility and the plaque index in polyarticular JIA (r=0.55, P=0.028).An association between IgG and rheumatic disease activity markers in JIA was evident. It is important to investigate the familiar periodontal status and clinical course in JIA, especially in enthesitis-related arthritis.