Background: Bicuspid aortic valve (BAV) increases the risk of thoracic-aortic dilatation/aneurysm and aortic dissection. In the pathogenesis of aortic aneurysm, matrix metalloproteinases have been found to play a role in the degradation of aortic wall proteins. Thus, this study aimed to investigate MMP2 and MMP9 gene polymorphisms in patients with BAV and ascending aortic aneurysm. Methods: Overall, 83 patients (36 patients admitted to the outpatient clinic and 47 controls) participated in this study. Genomic DNA was extracted from peripheral leukocytes using the MagNA Pure LC DNA Isolation Kit I on the MagNA Pure LC Instrument (Roche Applied Science). MMP2 (C1306T) and MMP9 (C1562T) gene polymorphisms were analyzed using the LightCycler(R) 480 High-Resolution Melting Master Kit (Roche Applied Science) with specific primers. Results: Both groups had similar sex distribution (p=0.601). Hypertension and smoking were more common in patients with MMP9 polymorphism (p<0.001; p=0.011). A statistically significant relationship was found between smoking, hypertension, and MMP9 gene expression. However, no significant relationship was noted between MMP2 and aneurysm diameter, hypertension, smoking, and antihypertensive drug use. Conclusion: Our findings indicate that increased aneurysm diameters and MMP9 gene polymorphism are potential predictors of aneurysm development in patients with BAV.