The dependence of cobalt ferrite nanosized powder production process on the synthesis method and conditions was studied. The paper shows the possibility for producing nanocrystalline CoFe₂ O₄ with an average particle size of 12 nm under conditions of an impinging-jets microreactor at room temperature. The influence exerted by the parameters of process implementation in the microreactor on phase formation in the CoO–Fe₂ O₃ – H₂ O system was analyzed.