Background: Leukocyte telomere length (LTL) has been revealed to be associated with aging-related diseases such as metabolic syndrome (MetS) and Type 2 diabetes mellitus (T2DM). We aimed to investigate the correlation of LTL with MetS and its components in T2DM patients in this cross-sectional study. Materials and Methods: A total of 344 T2DM patients were enrolled into this study. LTL was measured by Southern blot-based terminal restriction fragment length analysis. MetS was clinically defined by 2007 Chinese Guidelines on Prevention and Treatment of Dyslipidemia in Adults. Results: Of 344 T2DM patients, 53% had MetS. T2DM patients with MetS had significantly longer LTL than those without MetS (6451.95 +/- 51.10 base pairs vs. 6076.13 +/- 55.13 base pairs, P < 0.001), especially when T2DM patients had poor glycemic control (hemoglobin A1c >= 7%). Meanwhile, the trend of longer LTL was associated with the increased components of MetS in T2DM patient. Finally, LTL had a significant association with MetS (odds ratio [OR]: 2.096, 95% confidence interval [CI] 1.337-3.285, P = 0.001), low levels of high-density lipoprotein-cholesterol (HDL-C) (OR: 2.412, 95% CI 1.350-4.308, P = 0.003) in T2DM patients. Conclusion: T2DM patients with MetS had a significantly longer LTL than those without MetS. The longer LTL was especially evident in T2DM patients with poor glycemic control. Longer LTL was positively associated with MetS, particularly low levels of HDL-C in T2DM patients.