In this work, a simple solution combustion synthesis followed by heat treatment was proposed to produce nanocrystalline h-YbFeO3/o-YbFeO3 heterojunction and phase-pure o-YbFeO3. A detailed investigation on the formation process of h-YbFeO3 and o-YbFeO3 nanocrystals was carried out using a wide variety of methods, including EDS, SEM, PXRD, 57Fe Mössbauer spectroscopy, DRS. The most prospective samples of the h-YbFeO3/o-YbFeO3 nanocomposite and o-YbFeO3 nanopowder were examined towards the photo-Fenton decolorization of methyl violet (MV) under visible light. It was shown that the proposed approach allows for obtaining h-YbFeO3 and o-YbFeO3 nanocrystals with an average size of 15.7-21.1 nm and 41.1-65.5 nm, respectively, and with a specific surface area of up to 16 m2 g-1. It was found that the h-YbFeO3/o-YbFeO3 nanocomposite has a mesoporous structure and foam-like morphology, while the o-YbFeO3 nanopowder is non-porous and represented by agglomerates of individual nanoparticles with isometric morphology. Based on the DRS results, it was found that the band gap value was 2.05 eV and 2.16 eV for the h-YbFeO3/o-YbFeO3 and o-YbFeO3 samples, respectively, providing strong visible-light absorption of the samples. It was shown that the electron structure of the h-YbFeO3/o-YbFeO3 nanocomposite refers to I type heterojunction, leading to effective electron and hole transfer from o-YbFeO3 to h-YbFeO3 bands. This feature determines the higher photocatalytic activity of the h-YbFeO3/o-YbFeO3 nanocomposite as compared to pure o-YbFeO3 in the process of the Fenton-like decolorization of methyl violet under visible light with the pseudo-first-order reaction rate of 0.004848 min-1 and 0.003123 min-1, respectively. In conclusion, the mechanism of the photocatalytic decolorization of MV over the heterojunction nanocomposite was proposed to explain its high activity in the Fenton-like process. This journal is