For the majority of breast and/or ovarian cancer patients tested for BRCA1/2 genes, mutation screening of the coding regions remains negative. MicroRNAs which negatively regulate mRNA translation by binding to 3' untranslated region (3'UTR) are implicated in cancer. Genetic changes in the 3'UTR of several genes were reported to be associated with higher susceptibility to particular tumor types. The aim of this study was to analyze the BRCA1 3'UTR in patients tested negative for BRCA1/2 deleterious mutations, in order to find variants implicated in the decrease of BRCA1 expression through modification of miRNA binding. Genotyping analyses were performed on genomic DNA of 70 BRCA negatives index cases, selected among patients with breast or ovarian cancer, less than 50 years old, with a strong family history. The co-occurrence of the identified variants with deleterious BRCA1 mutations was then determined in a control population of 210 patients. A luciferase gene reporter assay was used to investigate the impact of the variants on the BRCA1 gene expression. Two novel variants, c.*750A>G and c.*1286C>A, were identified in the 3'UTR of BRCA1 gene, in two patients. The former was found three times in the control population, whereas the latter was absent. The used functional assay did not reveal any effect on the luciferase expression. This study reveals a weak genomic variability in the 3'UTR of the BRCA1 gene. All together, the results led us to classify the variant c.*750A>G as probably neutral, the variant c.*1286C>A remaining unclassified.