Well-defined titanium oxide–octadecylamine hybrid spherical particles (coefficient of variation (CV) ranged from 4 to 12%) were synthesized by sol–gel reactions with the aid of a flow reactor. The present synthesis consisted of two parts; (1) the initial stage of the reaction, which mainly concerned hydrolysis of titanium tetraisopropoxide (TTIP) and condensation, was conducted in the flow reactor, and then, (2) the solution after passing through the flow reactor was mixed with octadecylamine (ODA) in an aqueous 2-propanol mixture for the growth of titanium oxide–ODA hybrid particles. As for the initial stage, fast flow (2.5 to 40 mL min⁻¹) resulted in the formation of products with narrow particle size distribution (CV 4 to 7%), while slow flow (0.5 mL min⁻¹) led to the polydispersed particle formation (CV 27%) probably due to the growth/aggregation that occurred in the flow reactor. The particle size varied from ca. 70 to 900 nm by varing the composition of the batch reaction (the second step).