The effect of frequency and illumination intensity on the main electrical parameters such as ideality factor (n), zero bias barrier height (Phi(Bo)), depletion layer width (W-D), doping concentration (N-D) and interface state densities (N-ss) of Al-TiW-Pd2Si/n-Si structures have been investigated by using current-voltage (W) and admittance spectroscopy (C-V and G/w-V) techniques at room temperature. In addition, the dielectric constant (epsilon') and dielectric loss (epsilon ''), loss tangent (tan delta) and ac electrical conductivity (sigma(ac)) have been investigated using C-V and G/w-V measurements at various frequencies and illumination intensities. Experimental results show that both the value of capacitance (C) and conductance (G/w) increase with increasing illumination intensity and decreasing frequency. On the other hand the value of R-s decreases with increasing illumination densities. Also, the epsilon', epsilon '', tan delta and sigma(ac) values were found strongly frequency, bias voltage and illumination intensity. The results can be concluded to imply that the interfacial polarization can more easily occur at low frequencies and high illumination intensities consequently contributing to the deviation of electrical and dielectric properties of Al-TiW-Pd2Si/n-Si structures.