OBJECTIVES: To evaluate the extent of association between systemic inflammation and periodontal disease in American adults, and to assess whether socio-economic position mediated this relationship. METHODS: We used data from the National Health and Nutrition Examination Survey (NHANES IV) (2001-2010). Systemic inflammation was defined by individual and aggregate (cumulative inflammatory load) biomarkers (C-reactive protein, white blood cell counts, neutrophil counts, and neutrophil: lymphocyte ratio). Loss of attachment and bleeding on probing were used to define periodontal disease. Poverty:income ratio and education were indicators of socio-economic position. Covariates included age, sex, ethnicity, smoking, alcohol, and attendance for dental treatment. Univariate and multivariable logistic regressions were constructed to assess the relationships of interest. RESULTS: In a total of 2296 respondents, biomarkers of systemic inflammation and cumulative inflammatory load were significantly associated with periodontal disease after adjusting for age, sex, and behavioural factors. Socio-economic position attenuated the association between markers of systemic inflammation and periodontal disease in the fully adjusted model. CONCLUSION: Socio-economic position partly explains how systemic inflammation and periodontal disease are coupled, and may thus have a significant role in the mechanisms linking oral and non-oral health conditions. It is of critical importance that the social and living conditions are taken into account when considering prevention and treatment strategies for inflammatory diseases, given what appears to be their impactful effect on disease processes.