In this study, we have investigated the possibility of combining a cyclodextrin-containing polymer (CDP) with siRNA molecules to modulate gene expression in a light-directed manner through photochemical internalization (PCI) technology. We utilized S100A4 as a model gene to evaluate the efficacy of gene silencing. After optimization of carrier/cargo ratio and illumination dose, real-time reverse transcriptase-polymerase chain reaction data showed between 80% and 90% silencing in the siRNA samples treated with PCI compared with untreated control. In contrast, only a 0%-10% silencing effect was detected in the siRNA samples without PCI treatment, demonstrating the potency of light-specific delivery of siRNA molecules. Light-directed siRNA delivery was shown in 2 different cell lines with corresponding potency. Further, time-lapse results demonstrated maximum gene silencing only at 5 hours after endosomal release, implying, for example, rapid carrier decondensation when using the CDP. This work represents a first success in using a CDP delivery agent, without endosomolytic properties for siRNA gene silencing in a light-directed manner, opening the opportunity to use CDPs for light-directed siRNA gene silencing in vivo.