Microreactors can serve as advanced treatment units for end-of-pipe solutions in drinking water purification. They provide high surface-area-to-volume ratios and precise control over the reaction conditions, enabling a superior mass and heat transfer performance compared to that of conventional reactors. In the context of advanced oxidation processes, miniaturized flow reactors enhance the degradation efficiency for persistent pollutants by promoting effective mass transport under laminar flow conditions. The reduced diffusion distance between the aqueous phase and the immobilized catalyst layer minimizes mass transfer limitations. This effectively sorts out one of the main challenges associated with heterogeneous photocatalysis. Equally, nitrosamines are hazardous disinfection byproducts formed during water treatment when nitrogenous precursors react with chlorine or chloramine. Particularly, N-nitrosodimethylamine (NDMA) is among the most frequently detected nitrosamines, with a World Health Organization (WHO) guideline value of 100 ng/L in drinking water due to its carcinogenic potential. In this study, the degradation efficiency of a tandem microreactor system was evaluated. The system comprised two continuous-flow microreactors operated in series: the first consisted of a UV-irradiated column packed with TiO₂ immobilized on a biopolymeric matrix, while the second contained an activated carbon-packed bed. An aqueous NDMA solution (1 ppm, pH 3, 20 °C) was introduced under plug-flow conditions, with the temperature and pressure regulated via a Peltier module and a pressure control unit. NDMA degradation was monitored using liquid chromatography–tandem mass spectrometry (LC-MS/MS), revealing a removal efficiency of 87.6%.