The effect of pH on the nucleation stages of nickel electrodeposition on vitreous carbon has been analysed using low nickel concentrations, without additives. The experimental results indicated that there was a change in the electrochemical response of the system at 4 < pH < 4.5. A predischarge adsorption ascribed to nickel(II) species was observed with a different surface coverage depending on the pH. Moreover, different inhibition and 3D nucleation processes were detected in varying experimental conditions.