Breast cancer type 1 (BRCA1) gene also known as breast cancer type 1 susceptibility protein homologue plays important role in DNA double-strand break repair, homologous recombination, chromatin remodeling, cell cycle regulation and transcription regulation. Considering the importance of this protein, the present study was undertaken to analyse BRCA1 gene of different mammalian species by assessing the identity and similarity, phylogenetic relationship, physicochemical properties, predict the motifs, secondary and the tertiary structures. Seventeen nucleotide and protein sequences of BRCA1 gene of different mammalian species were retrieved from National Centre for Biotechnology Information (NCBI). Multiple sequence alignment was done using CLUSTAL W software, while identity and similarity was determined by constructing a pairwise comparison. Results obtained at the end of the experiment showed that there was no percentage Identity or similarity that was less than 70%. The phylogenetic relationship of BRCA1 gene of the mammalian species clustered into aquatic, herbivores, carnivores and omnivores, respectively. The highest time of divergence (95MYA) of the BRCA1 gene was observed between the BRCA1 gene of killer whale and human, while the least time of divergence (4.6MYA) was observed between the BRCA1 gene of cattle and American buffalo. Physicochemical properties of BRCA1 proteins in the five mammalian species (cattle, sheep, pig, American buffalo and human) were found to be unstable, hydrophilic and intracellular in nature. The following motifs were present at various positions in the BRCA1 gene of the five mammalian species; zinc finger RING, BRCT domain, N-myristoylation site, N-glycosylation, cAMP and cGMP dependent protein kinase phosphorylation site, Tyrosine kinase phosphorylation and cell attachment sequence, but leucin zipper pattern and microbodies c-terminal motifs were found in only human BRCA1 gene. The BRCA1 secondary structure contained the alpha helix, extended strand and random coil. Based on the results obtained, it can be deduced that BRCA1 gene has identical homologue, functional similarity and highly conserved in these mammalian species.