This study investigates the relationship between the Oxidative Balance Score (OBS) and all-cause and cardiovascular mortality in patients with diabetes and prediabetes. The OBS is a novel measure of systemic oxidative stress, reflecting the balance between pro-oxidants and antioxidants. Data from 10,591 participants in the National Health and Nutrition Examination Survey (NHANES) were analyzed over an average follow-up period of 99.8 months. The study found that higher OBS scores, indicating greater antioxidant exposure, were associated with lower risks of all-cause and cardiovascular mortality. Specifically, each unit increase in OBS was linked to a 1.8% decrease in all-cause mortality risk and a 4% decrease in cardiovascular mortality risk. Kaplan-Meier survival analysis and multivariable Cox regression models confirmed these findings, with the highest OBS quartile showing the lowest mortality rates. Subgroup analyses further validated the robustness of the relationship. The study highlights the importance of maintaining a diet and lifestyle rich in antioxidants to reduce mortality risks in individuals with diabetes and prediabetes.This study investigates the relationship between the Oxidative Balance Score (OBS) and all-cause and cardiovascular mortality in patients with diabetes and prediabetes. The OBS is a novel measure of systemic oxidative stress, reflecting the balance between pro-oxidants and antioxidants. Data from 10,591 participants in the National Health and Nutrition Examination Survey (NHANES) were analyzed over an average follow-up period of 99.8 months. The study found that higher OBS scores, indicating greater antioxidant exposure, were associated with lower risks of all-cause and cardiovascular mortality. Specifically, each unit increase in OBS was linked to a 1.8% decrease in all-cause mortality risk and a 4% decrease in cardiovascular mortality risk. Kaplan-Meier survival analysis and multivariable Cox regression models confirmed these findings, with the highest OBS quartile showing the lowest mortality rates. Subgroup analyses further validated the robustness of the relationship. The study highlights the importance of maintaining a diet and lifestyle rich in antioxidants to reduce mortality risks in individuals with diabetes and prediabetes.