Background: This study aims to provide basic data for minimizing exposure to secondhand smoke (SHS) by confirming the relationship between exposure to SHS and generalized anxiety disorder (GAD). Methods: Using the third year data of the eighth National Health and Nutrition Examination Survey, 3874 people were selected as subjects. Complex sampling analysis was applied to all analyses, and 307 people were exposed to the SHS group (SHSG) and 3567 people were not exposed to the SHS group (NSHSG). Complex sample linear regression analysis was conducted to confirm the effect of exposure to SHS on oral health and GAD. Results: Among oral-health-related factors, exposure to SHS in Korean adults was related to the presence of implants. Additionally, exposure to SHS had a significant effect on GAD despite adjusting for sociodemographic characteristics and oral-health-related factors (p< 0.05). Conclusions: In this study, the relationship between passive smoking and GAD was confirmed. Therefore, to reduce GAD, oral health management is necessary and exposure to SHS should be minimized.