AbstractA promising direction for improving proton exchange membrane fuel cells (PEMFCs) is the increase of their reliability and operating time without failure. Therefore, the problem of a reliable diagnostic tool is important. It has been theoretically deduced that a non uniform current distribution causes the increase of power spectral density of the flicker‐noise component of electrical fluctuations, which was experimentally confirmed for the case of excess humidification. Theoretical investigations allow to conclude that other reasons of current non uniformity, for example incorrect stoichiometry, can lead to similar results as well. Experimental findings show that the behavior and parameters of electrical fluctuations depend on the fuel cell operation mode and technical state of its components. This paper shows that electrical fluctuations reflect physical processes inside the fuel cell. Thus, the electrical fluctuations can be considered as a reliable diagnostics tool for PEMFC.