[en] A series of iron-doped KTiOPO₄ (KTP: Fe) single crystals in which iron substitutes for 0.1-0.3% titanium was grown. The structure of the KTP: Fe crystals was determined, and their dielectric and conducting properties were studied. An X-ray diffraction analysis failed to reveal such a small amount of Fe⁺³ ions in titanium octahedral positions of the structure. It was found that an increase in the iron concentration results in a lowering of the symmetry of Ti(1)O₆ and Ti(2)O₆ octahedra. The splitting of the dielectric anomaly due to the ferroelectric phase transition was explained by the mechanism of incorporation of an impurity into different growth pyramids of the crystals. It was established that the aging of the KTP: Fe crystals leads to changes in the permittivity and electrical conductivity during long storage