|Nanohybrid materials of OH-terminated fourth generation PAMAM dendrimer (DEN-OH) with graphene oxide (GO) and folic acid (FA) at different ratios of GO and DEN-OH were synthesized. The synthesized hybrids, GO/DEN-OH/FA, exhibited two photon absorption properties, since the excitation of these hybrids at 390 and 780 nm showed a strong fluorescence emission in the visible region at 450 nm. In addition, GO/DEN-OH/FA also had the ability to generate reactive oxygen species (ROS) upon laser irradiation. It was found that the fluorescence intensity of GO/DEN-OH/FA was markedly enhanced and no quenching of their fluorescence intensities was observed upon laser irradiation over 2 h. The bleb formation, the shrinkage and the irregularity in shape of HeLa cells were observed after laser irradiation at 780 nm on HeLa cells, which were incubated with GO/DEN-OH/FA. The reason is that under the laser irradiation GO/DEN-OH/FA can absorb NIR light and generate ROS, causing the HeLa cells’ death. Cell cytotoxicity measurement demonstrated that GO/DEN-OH/FA at the amount less than 20 µg/ml revealed low toxicity towards HeLa cells, as the cell viability was higher than 90%. Thus, owing to its two-photon absorption properties, the ability to generate ROS upon laser irradiation, and the low toxicity and high biocompatibility towards cells, these GO/DEN-OH/FA nanohybrid materials might have a potential to use as a fluorescence marker probe in therapeutic applications in living tissues and also could be utilized in photodynamic therapy for cancer treatment.