BACKGROUND: Oxidative stress plays a crucial role in the development of multiple chronic respiratory diseases. Oxidative Balance Score (OBS) composing of 16 dietary factors and 4 lifestyle factors has been developed to evaluate the effect of oxidants/antioxidants produced by dietary intake and lifestyle habits on the overall oxidative balance. However, the relationships between OBS with asthma, COPD, and asthma-COPD overlap (ACO) are still unclear. METHODS: A total of 10,942 adults aged 20 years and older from the 2013-2018 National Health and Nutrition Examination Survey were included in the analyses. ANOVA and chi-square tests were used to compare characteristics between different OBS subgroups. Multiple multivariate logistic regression was used to analyze the associations between OBS and asthma, COPD, and ACO.RCS curves were used to describe the dose-response effect of the associations. Subgroup analyses and interaction effects were employed to reflect the stability of the associations. RESULTS: In the fully adjusted models, OBS was found to be negatively associated with asthma, COPD, and ACO. OBS at Q2, Q3, and Q4 (OR: 0.66, 95% CI: 0.46-0.97) were negatively associated with the risk of asthma. OBS at Q2 and Q4 were negatively associated with the risk of COPD. OBS at Q2 and Q4 were negatively associated with the risk of ACO. The RCS curves reflected the negative dose-response trend of association. Moreover, the associations were stable in various subgroups. CONCLUSION: The negative associations between OBS and asthma, COPD, and ACO were found in American adults, providing evidence for dietary and lifestyle prevention.