Recent studies have suggested a strong association between chronic periodontitis and various chronic systemic diseases (condition), such as cardiovascular disease, diabetes, respiratory disease, adverse pregnancy outcomes, rheumatoid arthritis, certain types of cancer, and mental disorders. Although this relationship between periodontal and systemic diseases is still unknown, plausible biological mechanisms have been identified linking periodontal infection and these systemic diseases. For instance, periodontal bacteria can pass through the gingival epithelium and enter bloodstream and subsequently colonize other body parts, causing systemic inflammatory responses. Moreover, periodontal pathogens can induce local inflammation that releases pro-inflammatory cytokines or acute-phase proteins causing systemic inflammation. This mini-review provides an overview of the inflammatory and immune responses linking periodontitis with systemic diseases, particularly focusing on the microbiological aspects. To fully elucidate the mechanisms underlying this association, further research is required, but systemic health could be significantly improved by reducing the microbiological load of periodontal infection.