(Bi3.15Nd0.85)Ti3O12 (BNdT) thin films deposited by rf sputtering on Pt/TiO2/Si substrates demonstrate thickness dependences of electrical properties. The films exhibit well-established ferroelectric hysteresis loops with an almost thickness independent 2Pr of ∼23 μC/cm2 at 500 kV/cm. However, their nonvolatile polarization shows a monotonous decrease with increasing thickness at low operation voltages. Their coercive voltages exhibit an increase with increasing film thickness, which is accounted for by the existence of an interfacial nonferroelectric dead layer. Their dielectric permittivity demonstrates frequency and thickness dependent behavior, supporting the existence of the interfacial dead layer. The film thickness also affects both the reversible and irreversible components in the ac field dependence of relative permittivity.