The structural analysis of a historic masonry building is a topic of great interest and relevance. This study deals with the analysis of the Pieve San Lorenzo bell tower, a historically and artistically valuable and protected asset, located in Lunigiana, an area characterized by high seismicity. This research is divided into two phases. The first phase includes a detailed preliminary analysis of the bell tower, which encompasses historical studies, geometric surveys, damage assessment, identification of transformation phases, and material characterization. Diagnostic investigations were conducted during this phase to determine the modal parameters of the structure. The second phase focused on modeling the bell tower based on the experimental data collected. Two finite element brick and shell models were developed within the Mady computational code, specifically implemented for studying masonry structures. Once modal analyses were performed and the models calibrated, some preliminary static and time-history analyses were conducted to simulate the structure’s response to vertical loads and seismic actions. These analyses allowed for interpreting the observed damages, evaluating the bell tower’s behavior during seismic events, and testing the effectiveness of the numerical models used in the context of complex historic structures.