Hydrogen-induced pitting active sites on iron were investigated by electrochemical noise (EN) and scanning reference electrode techniques (SERT). The significant increase in the number of current and potential fluctuations in EN measurements indicates that hydrogen increases the number of active sites for formation of metastable pits, which are precursors of stable pits. The potential distributions over the surfaces of hydrogen charged and uncharged iron polarized at 0.07 V (vs. SCE) for different polarization times also show clearly that hydrogen significantly increases the number of pitting active sites on the surface of charged iron. It was also observed that to reach equal numbers of pitting active sites, a higher applied anodic potential is required on uncharged iron than on hydrogen-charged iron. The increase in the number of pitting active sites due to hydrogen was discussed in terms of the effect of hydrogen on the nature of the passive film and the dissolution rate of iron.