Dynamic identification plays a crucial role in understanding the behaviour of heritage structures, which often present significant uncertainties in their structural properties. Among available techniques, Operational Modal Analysis (OMA) has proven to be a particularly useful non-destructive tool for determining the dynamic characteristics of these buildings It provides insights into the global behaviour of the structure and supports the calibration of finite element models (FEM) for vulnerability assessment purposes. This study focuses on the dynamic identification campaign conducted on the Church of Santa Ana in Seville, Spain. As a significant example of historical constructions in southern Spain, the church presents complex structural and material characteristics that pose challenges for numerical modelling. The research details the OMA campaign, including sensor placement, measurement configurations, and data processing challenges. The collected experimental data were used to calibrate a model of the church, refining material properties and boundary conditions to achieve an accurate representation of its dynamic response. The combination of dynamic identification and numerical calibration allowed the assessment of essential aspects of the structural behaviour that were not easily detectable through simple visual inspection on-site, such as the quality of the connection between macroelements and the influence of the vaults' infill. The results provide valuable insights into the reliability of OMA for heritage buildings and its role in facilitating accurate structural analysis.