Structural assessment and maintenance of existing bridges attracted increasing attention in the scientific and engineering community after many recently occurred structural collapses. Following this trend, novel guidelines on risk assessment and monitoring of existing bridges have been issued, pointing out the primary role of Operational Modal Analysis (OMA) in enhancing the knowledge about the behavior of existing bridges, often in combination with model updating procedures to obtain a numerical model representative of the structural behavior in operational conditions. The application of OMA and model updating to a reinforced concrete arch bridge, characterized by two roadways at different elevations, resulting in a z-shaped deck, is discussed in the present paper. After introducing the case study, highlighting its main features, execution and results of the OMA test are presented and discussed. Finally, setting of the finite element model is illustrated; it is validated through quantitative comparisons between experimental results and numerical predictions.