Oxychlorination of ethene was performed over CuCl2/γ-Al2O3 catalyst in a microreactor (460 µm in diameter) and for comparison in a millireactor (1 cm in diameter). A copper-modified catalyst was prepared by a conventional evaporation–impregnation method without any promotors (e.g., K, Na, La) using copper (II) chloride as a precursor. The catalyst was characterized by nitrogen physisorption, Fourier transform infrared spectroscopy using pyridine, temperature-programmed desorption of CO2, scanning electron microscopy, energy-dispersive X-ray microanalysis, and transmission electron microscopy. Different reactor types led to notable differences in catalytic performance at the same partial pressures in terms of both activity and selectivity. A higher reaction rate was achieved in the microreactor, which was 4.5 times faster. The activity decline and different selectivity to the desired product are explained by a change in the oxychlorination mechanism due to a different ratio of reagents in the mixture during the reaction.