A glassy carbon (GC) electrode surface was modified with a cadmium pentacyanonitrosylferrate (CdPCNF) film as a novel electrode material. The modification procedure of the GC surface includes two consecutive procedures: (i) the electrodeposition of metallic cadmium on the GC electrode surface from a CdCl2 solution and (ii) the chemical transformation of the deposited cadmium to the CdPCNF films in 0.05M Na2[Fe(CN)5NO]+0.5M KNO3 solution. The modified GC electrode showed a well-defined redox couple due to [CdIIFeIII/II(CN)5NO]0/−1 system. The effects of supporting electrolytes and solution pH were studied on the electrochemical behavior of the modified electrode. The diffusion coefficients of alkali-metal cations in the film (D), the transfer coefficient (α) and the charge transfer rate constant at the modifying film|electrode interface (k s), were calculated in the presence of various alkali-metal cations. The stability of the modified electrode was investigated under various experimental conditions.