Estrogen receptor alpha (ERα) is one of the major sub-types of estrogen receptors. ERα plays an important rolein cellular proliferation and differentiation, chiefly in mammary tissues. In the present study we aimed to quantifyof ERα mRNA and protein expression in breast tissues from the Iranian population using a real-time PCR assay.Twenty nine breast tissues including 19 adenocarcinomas and 10 normal controls were recruited from the Iranianpopulation. mRNA extraction and cDNA synthesis were performed from these tissues using commercial kits.ERα mRNA and protein expression was quantified using real-time PCR and immunohistochemistry respectively.The results showed high expression of ERα mRNA (68%) and protein (53%) in the majority of breast cancertissues compared to normal breast tissues (p= 0.035). Also, high ERα mRNA was associated with tumour size ofbreast carcinomas. In this study, we first reported the expression of ERα in Iranian patients with breast cancersand demonstrated prevalence of the expression to be similar to breast cancers noted in other populations.