Neuronal progenitor cells (NPC) are particularly suited as the target population for genetic and cellular therapy of neurological disorders such as Parkinson's disease or stroke. However, genetic modification of these cells using retroviral vectors remains a great challenge because of the low transduction rate and the need for fetal calf serum (FCS) during the transduction process that induces the cell differentiation to mature neurons. To overcome these problems, we developed a new retrovirus production system in which the simplified retroviral vector GCDNsap engineered to be resistant to denovo methylation was packaged in the vesicular stomatitis virus G protein (VSV‐G), concentrated by centrifugation, and resuspended in serum‐free medium (StemPro‐34 SFM). In transduction experiments using enhanced green fluorescent protein (EGFP) as a marker, the concentrated FCS‐free virus supernatant infected NPC at a high rate, while maintaining the ability of these cells to self‐renew and differentiate in vitro. When such cells were grafted into mouse brains, EGFP‐expressing NPC were detected in the region around the injection site at 8 weeks post transplantation. These findings suggest that the gene transfer system described here may provide a useful tool to genetically modify NPC for treatments of neurological disorders.