Background <p>Numerous studies have demonstrated a significant association between serum copper (Cu) levels and abnormal glucose metabolism. However, there is a notable lack of research specifically examining the relationship between serum Cu concentration and type 2 diabetes mellitus (T2DM) in the elderly population. Consequently, this study aims to investigate the potential association between serum Cu concentration and T2DM in elderly adults.</p> Methods <p>A total of 565 participants were recruited from the outpatient and inpatient geriatric departments of the First Hospital of Jilin University between July 2021 and July 2023. Logistic regression models were employed to explore the association between serum Cu concentration and the risk of diabetes mellitus, with odds ratios (ORs) and 95% confidence intervals (95% CIs) calculated. Additionally, both smooth curve fitting and restricted cubic splines were utilized to assess the dose–response relationship between serum Cu concentration and T2DM.</p> Results <p>The results showed that serum Cu concentrations were higher in the T2DM group (17.5 ± 4.6μmol/L) than in the control group (16.6 ± 4.0μmol/L) (<i>P</i> = 0.021). After adjusting for potential covariates, the ORs (95% CI) for higher serum Cu levels were 1.00 (reference value), 1.66 (1.08–2.55), 2.07 (1.32–3.26), and 2.06(1.26–3.38) for T2DM, respectively. Both smooth curve fitting and restricted cubic spline curves showed a potential linear relationship between serum Cu concentration and T2DM (<i>P</i> for non-linear = 0.231 and <i>P</i> = 0.08).</p> Conclusion <p>This study suggests that T2DM in elderly adults is associated with increased serum Cu concentrations. Further prospective cohort studies in different populations are needed to validate our results.</p>