Nuclear membrane is one of the main barriers in polymer-mediated intracellular gene delivery. It was previously reported that glucocorticoid receptor dilated the nuclear pore and translocated into nucleus when it bound to its ligand, glucocorticoid. This suggests that the transport of DNA into nucleus may be facilitated by glucocorticoid. In this study, a glucocorticoid, dexamethasone, was conjugated to polyamidoamine (PAMAM) dendrimer and the effect of the conjugation was investigated. The PAMAM-Dexamethasone (PAM-Dexa) was synthesized by the one-step reaction using Traut's reagent. PAM-Dexa/plasmid DNA complex was completely retarded at a 1/1 weight ratio (polymer/DNA) in a gel retardation assay. PAM-Dexa protected DNA from DNase I for more than 60 min. PAM-Dexa/plasmid DNA complex showed the highest transfection efficiency to 293 cells at a 0.8/1 weight ratio. At this ratio, PAM-Dexa had higher transfection efficiency than PAMAM. Especially in the presence of serum during the transfection, the transfection efficiency of PAM-Dexa was higher than that of PAMAM or PEI by one order of magnitude. In addition, more PAM-Dexa/DNA complexes were observed in the nucleus region than PAMAM/DNA from the confocal microscopy studies. These results indicated that the technique with dexamethasone might be useful for the gene delivery using polymeric gene carriers and the development of efficient polymer vectors.