Gene therapy has opened doors for the treatment of genetic disorders such as cancer. However, it clinical application has been limited by safety-efficacy issues. Recently, dendritic stabilized metal nanoparticles have shown great potential as efficient non-viral modalities for plasmid DNA delivery. This study involved the synthesis, characterisation, evaluation of the cytotoxicity profiles, and ability of unmodified and folic acid modified poly(amidoamine) generation 5 dendrimer grafted gold nanoparticles to deliver plasmid DNA containing a luciferase gene to cancer cells in vitro. Unmodified and folic acid modified poly(amidoamine) generation 5 dendrimer nanoparticles were also evaluated for comparative studies. Nanocomplexes prepared with folic acid unmodified/modified poly(amidoamine) grafted gold nanoparticles and plasmid DNA were characterized by transmission electron microscopy, nanoparticle tracking analysis, ultra-violet spectroscopy, nuclear magnetic resonance, band shift, dye displacement and nuclease protection assays. Cytotoxicity profiles and gene expression were evaluated in five mammalian cell lines, using the MTT cell viability and luciferase reporter gene assays respectively. Nanocomplexes at optimum w/w ratios of 5.2:1 and 6.0:1, protected the plasmid DNA against serum nucleases and were well tolerated by all cell lines. Transgene expression was higher with folic acid modified dendrimer grafted gold nanoparticles, in folic acid-receptor overexpressing tested cells, compared to that of the control dendrimer nanoparticles, decreasing significantly (p <0.05) in the presence of excess folic acid ligand, confirming nanocomplex uptake to be via receptor mediation. Overall, the transfection efficiency of the dendrimer modified gold nanocomplexes superseded that of the control dendrimer nanocomplexes indicating the importance of dendrimer modification and the significant role of gold nanoparticles in the formulation of these delivery systems.