Objectives: The purpose of this study was to analyze the relations between general health status, oral health behavior, oral health status, and quality of life, as well as the mediating effects of oral health behavior and oral health status. Methods: Subjects aged ≥19 years participated in a health questionnaire in the third year of the Japanese National Health and Nutrition Examination Survey (2015). Results: Analysis of the overall path of periodontal disease showed that respiratory and circulatory diseases and oral health behaviors had statistically significant indirect effects on quality of life through the mediation of oral health behavior and oral health conditions, while analysis of the overall trend of the decayed, missing, and filled teeth (DMFT) index showed significant indirect effects on quality of life through mediation between oral and oral health conditions. As a result of these analyses, the association of general health status with quality of life, and its effect thereon, were confirmed through the intermediary of oral health behaviors and oral health conditions. Conclusions: Therefore, further research is needed on the relation of general diseases to oral health management. Special oral health departments need to be established in both general and university hospitals, and dental hygienists in charge of oral care need to be deployed to improve oral health for general diseases. Manuals and systems for oral health management and oral health promotion need to be developed for certified dental hygienists in Japan, specifically for each systemic disease. For example, hygienists should have guidance on the oral health practices that help in the prevention of diabetes.