The UV/H₂O₂ system is an effective advanced oxidation process (AOP) widely used for micropollutant abatement in drinking water and wastewater treatment plants. Recently, multiphysics simulations based on computational fluid dynamics (CFD) and chemical kinetics have shown promise by accurately depicting water treatment processes. This study demonstrates the feasibility of incorporating experimental results from a pilot-scale UV/H₂O₂ system into a multiphysics model. Various factors affecting contaminant degradation and oxidant production such as H₂O₂ dose, H₂O₂ injection methods, and reactor size were investigated. The obtained data became the basic building blocks when developing the numerical model. The model predictions exhibited a good correlation with the experimental results. 3-D visualizations using the model allow further in-depth analysis of the distribution of oxidants and target pollutant in the UV photoreactor, providing insights into the possibilities of reactor optimization.