Purpose <p>This study aimed to explore the association of the atherogenic index of plasma (AIP) and the risk of cardiovascular disease (CVD) as well as mortality risk in adults with diabetes or prediabetes.</p> Methods <p>A total of 12,189 individuals with a diagnosis of diabetes or prediabetes in the 1999–2018 National Health and Nutrition Examination Survey (NHANES) were included in our study. We investigated the connection between AIP and CVD risk through logistic regression analyses. Cox proportional hazard regression analysis was employed to assess the relationship of AIP with the risk of all-cause mortality and CVD mortality, respectively. Additionally, competing risk analyses were utilized to mitigate the impact of other causes of death on the association between AIP and CVD mortality risk. Restricted cubic spline (RCS) analyses were further conducted to evaluate the potential nonlinear correlation between AIP and the risk of CVD prevalence as well as CVD mortality.</p> Results <p>Logistic regression analyses revealed that elevated AIP was significantly and positively associated with the risk of most CVDs. Cox regression analyses demonstrated no statistically significant association between AIP and the risk of all-cause mortality or CVD mortality. However, after accounting for the influence of other competing causes of death via competing risk analyses, AIP exhibited a substantial positive association with CVD mortality risk. RCS analyses indicated that AIP was significantly and positively correlated with the risk of most CVDs. Furthermore, RCS analyses revealed a non-linear relationship between AIP and the risk of all-cause mortality, whereas a positive linear association was observed between AIP and CVD mortality risk.</p> Conclusion <p>Based on the findings of this study, individuals with diabetes or prediabetes may stand to benefit from the application of AIP in predicting the risk and prognosis of CVD.</p>