Herein, we report a new Prussian blue nanoparticle (PBNPs) incorporated polyvinyl alcohol (PVA) composite nanofiber (c-PBNPs/PVA) for the rapid adsorption of cesium (C-s) from radioactive wastewater. Initially, various electrospinning parameters such as solvent, PVA wt%, PBNPs wt% and glutaraldehyde (GA) wt% were extensively optimized to obtain a better physicochemical property of the c-PBNPs/PVA. In order to improve the water insoluble nature of the PVA, post cross-linking was carried out for the c-PBNPs/PVA using glutaraldehyde (GA) and HCl vapor as the cross-linker and catalyst, respectively. SEM images revealed the smooth and continuous morphology of the c-PBNPs/PVA composite nanofibers with diameters of 200-300 nm and lengths up to several millimeters. TEM images confirmed homogeneous dispersion and good incorporation of PBNPs into the PVA matrix. The amorphous nature of the c-PBNPs/PVA was confirmed by the XRD analysis. FT-IR spectra showed successful cross-linking of PVA with GA. It was found that the prepared composite nanofiber is highly hydrophilic and water-insoluble. The c-PBNPs/PVA showed an excellent and faster C-s adsorption rate of 96% after only 100 min. These results are comparable to those previously reported. After the C-s adsorption test, the c-PBNPs/PVA composite nanofiber can be easily separated from the wastewater.