Experimental studies of ammonia oxyethylation in a flow microchannel reactor are performed in broad ranges of temperatures (70–180°C) and residence times (0.47–3.3 min). The main products of the reaction between ethylene oxide (EO) and ammonia are monoethanolamine (MEA), diethanolamine (DEA), and target triethanolamine (TEA). It is shown that EO conversion grows along with residence time τ and reaches 90% at τ = 3.3 min. The highest selectivity toward MEA and DEA is observed at a temperature of 70°C and τ = 3.3 min. High selectivity toward TEA (84%) is achieved at short τ (0.47 min) and the maximum temperature (180°C). The TEA yield grows along with temperature and the residence time to reach 62% at τ = 3.3 min and temperatures of 155–180°C. Mathematical modeling of the ammonia oxyethylation process allows the kinetic constants of individual stages to be calculated. Differences between the obtained kinetic parameters and the literature data, due probably to using a microchannel reactor that ensures high parameters of heat and mass transfer instead of a traditional bulk triethanolamine synthesis reactor, are revealed.