Nanotechnology has emerged as a promising treatment strategy in gene therapy, especially against diseases such as cancer. Gold nanoparticles (AuNPs) are regarded as favorable gene delivery vehicles due to their low toxicity, ease of synthesis and ability to be functionalized. This study aimed to prepare functionalized AuNPs (FAuNPs) and evaluate their folate-targeted and nontargeted pCMV-Luc-DNA delivery in breast cancer cells in vitro. CS was added to induce stability and positive charges to the AuNPs (Au-CS), histidine (Au-CS-His) to enhance endosomal escape and folic acid for folate-receptor targeting (Au-CS-FA-His). The FAuNP:pDNA nanocomplexes possessed favorable sizes (<135 nm) and zeta potentials (<−20 mV), strong compaction efficiency and were capable of pDNA protection against nuclease degradation. These nanocomplexes showed minimal cytotoxicity (>73% cell viability) and enhanced transgene activity. The influence of His was notable in the HER2 overexpressing SKBR3 cells, which produced higher gene expression. Furthermore, the FA-targeted nanocomplexes enhanced receptor-mediated endocytosis, especially in MCF-7 cells, as confirmed by the receptor competition assay. While the role of His may need further optimization, the results achieved suggest that these FAuNPs may be suitable gene delivery vehicles for breast cancer therapeutics.