Objective: Hypertriglyceridemia (HTG), often but not always coexists with type 2 diabetes mellitus (T2DM). Both independently increase the risk of vascular complications, with inflammation serving as the underlying pathology. T-regulatory (Treg) cells, identified as CD4+CD25+forkheadbox-P3(FoxP3)+ cells, mitigate inflammation through secretion of interleukin(IL) 10. We investigated markers of Treg cell function in patients of T2DM with and without HTG. Methods: Patients with T2DM were divided into 2 groups: T2DM with normal triglyceride (TG) levels (n=30), designated as (DNT) and T2DM with HTG (n=30) designated as (DHTg).Expression of the FOXP3 and IL-10 genes were evaluated using quantitative polymerase chain reaction. Serum soluble CD25 (sCD25) levels were measured by enzyme-linked immunosorbent assay. Results: FOXP3 and IL-10 expressions were reduced in DHTg group. Serum sCD25 levels were significantly higher in the DHTg group (p=0.04). FOXP3 and IL-10 expressions correlated positively in both groups. FOXP3 and IL-10 expression were reduced in both DHTg-normal body mass index (NW) and DHTg-overweight and obese (OwO) compared with respective DNT subgroups, although difference was smaller among OwO groups. Conclusion Reduced expression of FOXP3 and IL-10 indicates compromised Treg function in patients with T2DM and HTG. This impairment may contribute to inflammatory stress, thereby increasing the risk of atherosclerosis. Elevated serum sCD25 levels may represent an additional link between TG and immune imbalance. Obesity also appears to influence Treg function, though its precise role remains uncertain. Aggressive management of HTG in T2DM is warranted. Furthermore, Tregs may represent an attractive therapeutic target for mitigating risk of complications.