In this study, vibration characteristics of flexible four-bar mechanisms are investigated by using the procedure developed in ANSYS. Kinematics and kinetics of the four-bar mechanism having rigid and flexible links are presented for finite element modelling of the flexible mechanism. Equations of motion for rigid and flexible four-bar mechanisms are derived by using Lagrangian dynamics to show the theoretical approach. In order to find the natural frequencies of the flexible four-bar mechanism for different configurations, eigenanalysis of the mechanism is carried out by considering the discrete crank positions. Dynamic natural frequencies based on the motion induced axial loads are found by using the discrete inertia forces acting on the nodes of the finite element model. The mode shapes of the flexible four-bar mechanism are also found and plotted with undeformed configurations.