Background <p>Obesity is a well-established risk factor for T2DM, and various obesity-related indices have been developed to assess the relationship between obesity and the disease. Traditional indices such as body mass index (BMI) have certain limitations in accurately predicting the risk of T2DM. Therefore, exploring new obesity indices is of great importance for the early prevention and management of T2DM. This study aims to investigate the association between the new obesity index, weight–adjusted waist circumference index, and type 2 diabetes.</p> Objective <p>The Weight-adjusted Waist Index (WWI) is a novel obesity assessment indicator. The purpose of this study is to explore the correlation between WWI and type 2 diabetes mellitus (T2DM).</p> Methods <p>This study is a cross-sectional study, using the community diabetes screening data from the Yichuan Street Community Health Service Center in 2023, to conduct a multivariate regression analysis and linear fitting curve analysis on 747 participants. Data collection was carried out through standardized questionnaires and physical examinations. All the subjects were divided into 4 groups according to the quartiles of WWI. The general information and clinical characteristics of the four groups of research subjects were compared. The linear relationship between WWI and T2DM was analyzed by using the linear fitting curve. The association between the WWI of patients and the risk of developing type 2 diabetic nephropathy was analyzed via logistic regression. </p> Results <p>After fully adjusting for confounding factors, WWI was associated with an increased risk of T2DM.The linear fitting curve showed a non-linear positive correlation between WWI and T2DM. When WWI is greater than 10.4&#xa0;cm/√kg, the incidence of T2DM will greatly increase. The result of multivariate logistic regression analysis suggested that an increase in WWI was significantly associated with an elevated risk of T2DM (OR = 1.736, 95% CI: 1.203–2.584), with a significant interaction effect (<i>p</i> = 0.004).</p> Conclusion <p>WWI is positively correlated with T2DM, and this study shows that WWI plays an important role in the prevention and management of T2DM.</p>