Obesity is reported to be associated with an increased incidence and prevalence of periodontal disease. The present study aimed to evaluate the relationship between oral health behaviors and obesity in South Korean adults. Data from the Korea National Health and Nutrition Examination Survey between 2008 and 2010 was used to assess this and a total of 15,666 participants were included in the analysis performed. Oral behaviors, including the time of day and rate of tooth brushing, and usage of secondary oral products, were considered in this analysis. Obesity was defined using the following three methods: Body mass index, waist circumference and percentage body fat (PBF). Hierarchical multivariable logistic regression analyses were performed to determine the association of oral health behavior with obesity after adjusting for possible confounding variables. The frequency of daily tooth brushing and usage of secondary oral products was lower in individuals with obesity, irrespective of the method used to define obesity. Conversely, the risk of general obesity, abdominal obesity and high PBF was higher in individuals with a lower daily frequency of tooth brushing and usage of secondary oral products.