The current transport mechanisms in undoped hot filament chemical vapor deposited (CVD) diamond films were investigated by employing impedance spectroscopy. An electrical model has been proposed to explain different conduction mechanisms. AC conductivity plots showed that there are at least two mechanisms involved in the carrier transport in polycrystalline diamond films. Hopping transport along the grain boundary path is the major component, while the interface states between the grain crystallites play a significant role in the low-frequency regime below 10 Hz.