Hypertrophic cardiomyopathy (HCM) is a genetic disease of the myocardium that is characterized by phenotypic variability among patients. miR-146a is a small non-coding RNA that is well known for its role in inflammation and myocardial hypertrophy. The aim of this study is to evaluate the role of miR-146a as a candidate genetic factor influencing HCM phenotype. In this study, 140 HCM patients and 112 control individuals were genotyped for the rs2910164 single nucleotide polymorphism (SNP) in the MIR146A gene; using this data, the correlation between different genotypes and clinical features of the disease were determined. Additionally, plasma levels of miR-146a-5p were determined in 50 HCM patients and 30 control individuals by using qPCR. The incidence of GC and CC genotypes were significantly lower in HCM patients (odds ratio (OR)=0.5 [0.3-0.8], p=0.007). The GC/CC genotypes in the dominant genetic model positively correlated with the presence of left ventricle outflow tract (LVOT) obstruction (OR=2.3 [1.2-4.7] and p=0.018), a higher left ventricle mass index (118±47g/m2 vs 92±42g/m2 and p=0.02), and increased left ventricle end-diastolic diameter (4.66±0.64cm vs 4.39±0.7cm and p=0.026). Atrial fibrillation was significantly higher in patients homozygous for the C allele (OR=10.6 [2-55], p=0.003). Interestingly, the plasma levels of miR-146a-5p were significantly increased in HCM patients with LVOT obstruction. Our findings indicate that the C allele of the rs2910164 SNP might be under negative selection in HCM patients. Additionally, plasma levels of miR-146a-5p and GC/CC genotypes are indicative of the obstructive phenotype in HCM patients.