Background/aim: A variation in the 3 prime untranslated regions (3?-UTRs) affects the binding of microRNA (miRNA) to the breast cancer (BC) susceptibility gene 1 (BRCA1) gene, and thus regulate its expression. In this study, the consequences of a variation in the miRNA-binding site (rs8176318G>T) in the 3?-UTRs of BRCA1 and its association with the risk of BC were investigated.Materials and methods: The selected variation (rs8176318G>T) was genotyped in BC patients (n = 300) and healthy controls (n = 300) using allele-specific polymerase chain reaction (PCR) [tetra-primer amplification refractory mutation system-PCR (T-ARMS-PCR)]. The results of the T-ARMS-PCR were further confirmed by Sanger sequencing through a random selection of 10% previously analyzed samples by T-ARMS-PCR. Association of this variation with BC was tested by calculating the odds ratio (OR) (at 95% CI) and ?2-value using 4 different genetic models (codominant, dominant, recessive, and additive models). Results: Using Fisher?s exact test, a significant association between variant rs8176318 (G>T) and BC was found in codominant [?2-value = 15.68, df: 2 P