A diverter damper has been commonly used where the gas is either to be directed to alternate outlets or enters the system from alternate inlets. For combined cycle power plant, the diverter damper is used to direct exhaust gas of the gas turbine either into the waste heat recovery boiler or, when running under open cycle mode, exits directly to the by-pass stack. The damper also allows controlling proportion of flow entering the boiler. In a combined-cycle power plant in Malaysia, there have been significant problems with structural integrity of the diverter damper. Thus work was undertaken to understand and determine the cause of the failure of the damper. One of the possible cause of the failure is flow induced vibration. This paper describes Computational Fluid Dynamics (CFD) analysis that has been done to investigate the possibility. The results of the analysis shows that there is a possibility of flow induced vibration especially at near fully closed position. The frequency of the periodic vortex shedding was found to be close to the second fundamental natural frequency of the damper. Thus, resonance may be induced and may have been responsible for the failure of the damper. Suggestions on how to overcome the problem are also given.