Flow microchannel reactor was used to study the synthesis of iminodiacetic acid (IDA) via the catalytic oxidative dehydrogenation of diethanolamine (DEA) over catalyst Cu/ZrO2 (containing copper in amount of 10 mass%) at various residence times, reaction temperature ranging within 160–190 °C. IDA was shown to form in the course of two consecutive reactions through intermediate compound N-(2-hydroxyethyl)glycine (HEG). DEA conversion and IDA yield were found to increase as residence time and reaction temperature grow, meanwhile HEG concentration maximum on kinetic curves shifts towards shorter residence times. Effective reaction rate constants were determined according to the suggested scheme of IDA synthesis. Calculated activation energies for two consecutive stages of IDA synthesis were found to be 73.7 and 67.2 kJ/mol, respectively.