We have produced ultra-small sized (20–50 nm diameter) calcium phosphate (CaP) nanoparticles encapsulating a reporter gene, pCambia 1301. The material in the nanoparticles is of crystalline nature having a hydroxyapatite structure as revealed from the XRD pattern. The maximum loading of pCambia 1301 in the nanoparticles and the pH-dependent dissolution of CaP nanoparticles were studied using gel electrophoresis. DNA is highly protected in the cell from cellular nucleases when it is encapsulated into the CaP nanoparticles. The transformation efficiency was found to be about 80.7% compared to 54.4% by Agrobacterium tumefaciens and only 8% using naked DNA. Our results indicate that CaP nanoparticles could be used as a better transforming vector in plants as compared to the Agrobacterium tumefaciens mediated genetic transformation technique. In our experiment we presume that the plasmid DNA released from CaP nanoparticles in the cell has, perhaps, been able to enter into the nucleus. Transgenic GUS (β-glucuronidase) integrates into the genomic DNA by non-homologous recombination as in the case of Agrobacterium tumefaciens infection. Because of high transformation frequency, the method seems to be an attractive option for delivering a transgene into plant cells and protoplast.