Breast cancer therapy is rapidly evolving from traditional treatment modalities toward precision nanomedicine-based strategies that integrate molecular genetics with targeted, smart delivery systems. This chapter provides a comprehensive review of current and emerging nanotechnological approaches to breast cancer therapy, beginning with the molecular underpinnings of the disease. We explore the genetic landscape of breast cancer, including the roles of oncogenes, tumor suppressor genes, and regulatory RNA molecules, with a focus on the therapeutic applications of small interfering RNA (siRNA), microRNA (miRNA), and antisense oligonucleotides (ASOs). Challenges associated with RNA-based therapeutics, such as extracellular and intracellular delivery barriers, are addressed alongside innovative strategies for overcoming these limitations—particularly through nanoparticle-mediated delivery systems, chemical modifications, and tissue-specific targeting. The chapter delves into the development of lipid-based, polymeric, inorganic, and hybrid nanocarriers designed to improve bioavailability, targeting precision, and endosomal escape of nucleic acid drugs. We further examine synthetic organic nanostructures such as carbon dots (CDs), liposomes, and polymeric nanoparticles, discussing their applications in drug delivery and theranostics. The multifunctional nature of CDs in delivering chemotherapeutic agents, enhancing imaging, and overcoming resistance mechanisms is highlighted. Targeted nanomedicine approaches, including photothermal therapy (PTT), photodynamic therapy (PDT), and magnetic nanoparticle-assisted treatments, are presented as promising tools for localized and stimuli-responsive drug release. Overall, this chapter underscores the interdisciplinary convergence of molecular genetics, nanobiotechnology, and advanced drug delivery systems in developing next-generation therapeutics for breast cancer. These innovations represent a critical step toward personalized, efficient, and minimally invasive cancer therapy.