The exploration of messenger RNA (mRNA) as a potential therapeutic regulator of gene expression has been significantly reduced by the inability of polyplexes to escape the endocytic pathway, combined with the lack of specific targeting. In the present study, we have developed a site-specific delivery strategy for mRNA molecules through the use of photochemical internalization (PCI) technology. When using EGFP mRNA as a model system, a 10- to 40-fold increase in EGFP-positive cells was obtainable in PCI-treated samples, compared to untreated PCI samples in a human osteosarcoma cell line. The amount of EGFP-positive cells in both PCI and non PCI-treated samples were highly dependent on the nitrogen/phosphate (N/P) ratio. Potent delivery of mRNA molecules through the endocytic pathway by the use of polyplexes and PCI was achievable without any loss of cell viability. The main benefit of the strategy proposed is the possibility for protein production from the delivered mRNA in a way that is controllable in a time- and site-specific manner.