In this work, a BiFeO₃ film is prepared via a facile sol–gel method, and the effects of the relative humidity (RH) on the BiFeO₃ film in terms of capacitance, impedance and current–voltage (I–V) are explored. The capacitance of the BiFeO₃ film increased from 25 to 1410 pF with the increase of RH from 30% to 90%. In particular, the impedance varied by more than two orders of magnitude as RH varied between 30% and 90% at 10 Hz, indicating a good hysteresis and response time. The mechanism underlying humidity sensitivity was analyzed by complex impedance spectroscopy. The adsorption of water molecules played key roles at low and high humidity, extending the potential application of ferroelectric BiFeO₃ films in humidity-sensitive devices.