Decontamination effectiveness of ammonium-ferric(III)-hexacyanoferrate(II) (AFCF) in reducing the radiocaesium transfer to hen eggs was examined. The albumen activity concentration for ¹³⁷Cs was higher than that in egg yolk. The most effective reduction of radioactivity concentrations in all egg components was noted in birds treated with hexacyanoferrate from the first day of radioisotope administration. Radioactivity concentrations in hens treated simultaneously with ¹³⁷CsCI and a caesium binder were lower by >90% than those in the controls at selected measurement intervals. The decontamination efficiency lowered with the delayed AFCF treatment.