The kinetics of the iron electrodeposition reaction from a plating bath containing trivalent iron ions is investigated in the present work. The electrochemical reaction is stated to proceed via the formation of relatively stable intermediates: Fe(II) ions. Only a part of the total amount of Fe(II) ions formed at the first stage of Fe(III) discharge is reduced further, producing metal iron. The effect of polyhexamethyleneguanidine hydrochloride (with an average molecular weight of 1000) on the iron deposition is ascertained. The presence of polymer additive in the iron electrolyte appreciably affects the rate of iron deposition, while the polymer additive does not influence the rate of Fe(III) ions discharge. The effect of polyhexamethyleneguanidine on the rate of iron electrodeposition is discussed in terms of the influence of the oligomer on the aggregative stability of the Fe(OH)(3) sol formed in the near-electrode layer.