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The present study was conducted to prepare precursors by rapid hydrolysis method for realizing lower temperature formation of NiFe2O4 under hydrothermal conditions. The precursor, obtained from a lower concentration of NiCl2–FeCl2 mixed solution, was almost amorphous and could be easily converted to NiFe2O4 crystal phase at around 130°C by hydrothermal treatment. On the other hand, when a higher concentration of NiCl2–FeCl2 solution or trivalent iron salt (FeCl3) was used as starting reagents, individual crystal phases such as α-Ni(OH)2, γ-Fe2O3 and α-FeOOH were recognized in precursors owing to the difference in hydrolysis rates between Ni2+ and Fe2+ (or Fe3+). These individual crystal phases involved precursors that could not be converted easily to NiFe2O4 crystal phase, but needed to treat at higher temperatures for forming NiFe2O4 at least 200°C. Thus, the co-existence of individual crystal phases in precursors might prevent the amorphous precursor from forming NiFe2O4 crystal phase. The formation of NiFe2O4 at lower temperatures is considered to be taken place preferentially from amorphous precursors than individual certain crystal phases. [ABSTRACT FROM AUTHOR]