Background <p>Treatment adherence is a key issue in type 2 diabetes mellitus and may be influenced by diabetes-related stigma, but evidence on this relationship is limited.</p> Objectives <p>To explore the relationship between diabetes-related stigma and treatment adherence among adults with Type 2 Diabetes Mellitus.</p> Methods <p>This cross-sectional study was conducted at the endocrinology clinic of a publicly funded hospital in Turkey from June 2023 to February 2024. A total of 308 adults with T2DM were recruited through convenience sampling. Data were collected using a sociodemographic and clinical characteristics form, the Type 2 Diabetes Stigma Assessment Scale, and the Type 2 Diabetes Mellitus Treatment Patient Compliance Scale. Hierarchical multiple linear regression analyses were conducted to identify predictors of treatment adherence.</p> Results <p>The mean stigma total score was 46.31 ± 12.35, and the mean treatment adherence score was 72.44 ± 12.11. Higher diabetes stigma scores were significantly associated with higher treatment adherence scale scores, indicating poorer treatment adherence (<i>r</i> = 0.193, <i>p</i> &lt; 0.001). In the final regression model, total stigma was a significant predictor of treatment adherence (β = 0.144, <i>p</i> = 0.017), together with self-care ability and alcohol consumption, explaining 9.2% of the variance (Adjusted R²= 0.092).</p> Conclusion <p>Results suggest that diabetes-related stigma may be associated with treatment adherence among adults with type 2 diabetes mellitus. Total stigma emerged as a significant predictor of treatment adherence in the multivariate model, together with self-care ability and alcohol consumption. These findings suggest stigma may be an important consideration in diabetes management.</p>