In this study, dynamic characteristics of a prototype arch dam-reservoir-foundation model are determined by operational modal analysis method using frequency and time domain techniques. For this purpose, a prototype arch am-reservoir-foundation model is constructed in laboratory conditions. Ambient vibration tests were conducted to the arch dam to identify its natural frequencies, mode shapes, and damping ratios. Natural excitations such as small impact effects were used to vibrate the arch dam. Sensitivity accelerometers were used to collect signals from the measurements. Measurements were recorded for empty and full reservoirs. The signals collected from the tests were processed by operational modal analysis software, and the dynamic characteristics of the dam were estimated using enhanced frequency domain decomposition and stochastic subspace identification techniques. The dynamic characteristics obtained from both techniques are close to each other. It can be stated that the both enhanced frequency domain decomposition and stochastic subspace identification techniques are very useful to identify the modal parameter of the prototype arch dam. In addition, it is observed that there is 20–25 % difference between natural frequencies for empty and full reservoirs.