Objective: Breast cancer is one of the most common health problems. It has been suggested that several risk factors, either considered as external or internal, play a critical role in the pathogenesis of breast cancer, which among them, HERV-k, has the most fundamental role. In the present study, we aimed to evaluate the role of HERV-k env, gag, rec, np9 expressions in breast cancer progression. Materials and methods: We collected 40 breast cancer tissues and their normal adjacent ones. After extracting the RNA of breast samples, we evaluated the expression of HERV-k env, gag, rec, np9 by using Quantitative real-time PCR (qRT-PCR). Results: The resulting data revealed that while there was a meaningful increase in the expression level of HERV-k env, gag and np9 in breast cancer tissues (P ≤ 0.01, 0.05, 0.05, respectively), we failed to find any significant elevation in the expression level of rec mRNA level. Conclusion: The results of our study suggested that there is a plausible correlation between the mRNA expression level of HERV-K env, gag and np9 and the progression of breast cancer, proposing these markers as promising biomarkers to diagnose breast cancer.