Biogenic synthesis of gold nanoparticles using plant extracts has been widely explored for biomedical applications due to its eco-friendly and cost-effective nature. In this study, gold nanoparticles were phytoformulated using an ethanolic extract of dwarf copper leaf. Their physicochemical properties, antineoplastic activity against MCF-7 breast cancer cells, and bactericidal efficacy against selected pathogenic microorganisms were systematically evaluated. The phyto-synthesized AuNPs show potential as an antineoplastic agent, significantly dropping the viability of MCF-7 breast cancer cells when administered at higher concentrations. Comprehensive characterization revealed that the phyto-formulated AuNPs were predominantly spherical with sizes ranging from 15–38 nm as observed by TEM, while XRD analysis confirmed their crystalline nature. Furthermore, FT-IR analysis determined the plant extract’s functional groups, which served as both reducing and stabilizing agents during synthesis. Additionally, the phyto-formulated AuNPs showed bactericidal efficacy against several microorganisms, including Bacillus cereus, Salmonella typhimurium, Staphylococcus epidermidis, and Serratia species. Particularly, the phyto-formulated AuNPs were effective against B. cereus and Serratia species. The present results showed that the phyto-formulated AuNPs could be used in biomedical contexts for bactericidal action and medication delivery. By using this cost-effective and eco-friendly nanobiotechnology method, AuNPs can enhance drug delivery and efficacy with lower toxicity effects associated with conventional chemotherapies.