The frequency-dependent dielectric dispersion of a thin film of poly(vinyl alcohol)/ hydroxypropyl cellulose (80/20 wt/wt%) blend prepared by the solution-cast technique is investigated in the frequency range 1-100 kHz. The effect of different fast neutron fluencies in the range 105-108 n/cm2 on the prepared film is also studied. Dielectric relaxation has been analyzed based on the examination of the wide range of molecular mobility of the amorphous phase of the blend system. The obtained results noticed that, measureable changes in the behavior and values of the dielectric properties are detected. These changes may be attributed to degradation and/or crosslinking process by the presence of HPC with PVAor by the irradiation with fast neutron which may be suggested that the observed dispersion depends on composition and irradiation of the blend matrix.