Introduction: Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by the incapability of pancreas to increase insulin secretion to compensate for insulin resistance in the peripheral tissues. T2DM is a multifactorial disease including several environmental factors with the presence of genetic predisposition. The transcription factor 7-like-2 gene ( TCF7L2) rs7903146 (C/T) polymorphism is one of the most susceptible genes to T2DM discovered to date, with contribution to the disease through the Wnt/β-catenin signaling pathway affecting pancreatic islet development, expression of several genes involved in insulin granules exocytosis, and the incretin glucagon-like peptide 1 ( GLP-1) gene. Then, TCF7L2 gene seems to affect diabetes susceptibility through B-cell dysfunction that is why we studied its association with T2DM in particular. Objectives: To investigate the potential association of the transcription factor 7-like-2 ( TCF7L2) rs7903146 (C/T) gene polymorphism in patients with T2DM. Methods: A case-control study conducted on 70 T2DM patients recruited from the endocrinology clinic at Ain Shams University Hospitals, and 30 non-diabetic healthy controls age- and sex-matched with the patients. All subjects underwent full history taking; thorough clinical examination; routine laboratory investigations including hemoglobin A1c, total cholesterol, triglycerides, high-density lipoprotein-cholesterol, and low-density lipoprotein-cholesterol; and determination of TCF7L2 gene polymorphism by qRT-PCR. Results: The minor T allele of the rs7903146(C/T) SNP was associated with high risk of development of T2DM with an OR of 1.35 (95% CI: 0.68–2.6) and the heterozygous genotype (CT) with an OR 1.16 (95% CI: 0.49–2.7); however, they were statistically insignificant ( p value >0.05). Conclusion: Our study did not confirm the presence of significant association between the TCF7L2 rs7903146(C/T) polymorphism and T2DM; however, it pointed out the possibility of presence of high risk of development of T2DM in patients with TT genotype. Further studies with higher sample size are needed to clarify the association.