Prussian blue (PB) particles were successfully immobilized on a novel chitosan membrane. Morphological observations confirmed that the PB particles were densely immobilized within the membrane. From isothermal adsorption analysis, an increase in the mass fraction of PB contained within the membrane (MFPB) assisted the improvement of the initial adsorption rate as well as the adsorption uptake of cesium ions. A high MFPB led to a decrease in the effective diffusion coefficient of cesium ions in the membrane. Adsorption equilibrium data were found in good agreement with the Langmuir model. The maximum adsorption capacity of the membrane immobilizing PB as well as the adsorption constant in the Langmuir model increased with higher MFPB.