This paper presents results of an experimental modal analysis of prestressed concrete sleepers in both free-free and in-situ conditions. Four types of prestressed concrete sleepers were provided by the Australian manufacturers. The concrete sleepers were tested using an impact hammer excitation technique over the frequency range of interest: 0 to1600 Hz. Frequency response functions (FRFs) were measured using the Bruel&Kjaer PULSE dynamic analyser. The FRFs were processed using the STARModal analysis package to identify natural frequencies and the corresponding mode shapes for the sleepers. The conclusions are presented on the effect of boundary conditions on the dynamic properties of prestressed concrete sleepers and their use for predicting railway track dynamic responses. Vibration parameters of concrete sleepers are required for the development of a realistic dynamic model of railway track capable of predicting its responses to impact loads due to wheel burns, irregularities of the rail, so on.