A significant portion of Italian and European infrastructure consists of masonry arch bridges, many of which were constructed before the 20th century. These structures are particularly vulnerable to seismic loads and, over time, have exhibited several issues such as material deterioration, lack of maintenance, and increased service loads. This study investigates the dynamic behavior of a masonry arch bridge inspired by an existing 18th-century structure located in Southern Italy. Since 2019, the bridge has been part of the Seismic Observatory of Structures network and has been continuously monitored by the Italian Civil Protection Department. The recorded data have enabled the identification of the structure natural periods and corresponding mode shapes. A three-dimensional numerical model is developed within the software 3DEC, using a discrete element approach. The model includes both structural and non-structural components, such as piers, abutments, backing, spandrel walls, and backfill material. The numerical results, obtained through eigenvalue analysis and dynamic identification, are compared with experimental data. Different boundary conditions for piers and abutments are also examined to assess their influence on the bridge behavior. Finally, sensitivity analyses are conducted to evaluate the impact of modeling choices on both the accuracy of the results and computational efficiency.