This paper presents the results of an investigation on the dielectric properties and discusses the observed ac and dc electrical characteristics of aluminum oxide thin films. ac properties are deduced from the capacitance measurements at intermediate and high frequencies. Measurements indicate the existence of two relaxation mechanisms. Hopping polarization of charge carriers is responsible for the high‐frequency dissipation mechanism. This polarization is influenced by an additional mechanism at low frequencies. dc current‐voltage characteristics are obtained from the steady‐state region of the current transients for various step voltages. They exhibit two distinct types of conduction mechanisms depending on the applied voltage: (a) Ohmic conductivity at low voltages and (b) space‐charge‐limited current (SCLC) at high voltages. Specimens are polarized in the upper limit of the Ohmic region. According to the additional effect of the polarization field in a formed sample with respect to applied field, two alternative types of current transients are posible, which are called ’’same’’ and ’’reverse’’ polarity transients. Relaxation frequencies, obtained by means of the current transient data using Hamon’s equation, depend on the applied electrical field. The polarization field also moderates the relaxation frequencies.