Breast cancer (BC) is a multifactorial disease where microRNA (miRNA)-mediated dysregulated gene expression plays a pivotal role in tumorigenesis, progression, and clinical outcomes. Genetic variation, particularly SNPs in miRNA sequences and the 3' untranslated regions (3'UTRs) of their target genes, can disrupt miRNA-mRNA interactions, leading to altered gene expression. Despite several existing databases providing insights into various aspects of miRNAs and their target genes in association with the development of the disease. Still, there remains a critical gap in a unified, BC-specific repository that integrates SNPs in miRNAs, their target genes, and associated molecular mechanisms. To address this, we developed BreVamiR3' (Breast cancer-associated genetic Variations in miRNA and 3'UTR of their target genes), a novel, freely accessible database (https://brevamir3.web.app/index.html). BreVamiR3' features comprehensive and curated data on 500 miRNAs and 828 target genes associated with BC, including experimentally validated SNPs, chromosomal loci, expression profiles, BC subtypes, signaling pathways, and classifications of genes i.e. oncogene, tumor suppressor, or both. Unique features of BreVamiR3' include detailed annotations of SNPs disrupting miRNA-target interactions, subtype-specific miRNA expression, visualization of miRNA-chromosomal distributions and their experimental validation. Chromosome 19 harbours the highest number of BC-associated miRNAs, while target genes such as CCND1, KRAS, and ERBB2 demonstrate extensive miRNA regulation. By integrating genetic variations with functional and clinical relevance, BreVamiR3' provides a single platform to explore miRNA-mediated regulatory networks, their genetic variation, and downstream signaling pathways in BC. This database serves as a powerful resource for researchers, enabling exploration of miRNA-gene interactions, genetic variation, and their role in pathogenesis of BC and diverse clinical outcomes.