In this study, the root causes of failure in the third-stage stator and the fourth-stage rotor blade of a gas turbine after 720 hours of operation were investigated. The initial fracture led to extensive damage to the remaining stationary and rotating blades. Fractographic examination and microstructural characterization were carried out using optical microscopy (OM) and scanning electron microscopy (SEM). The results revealed that the primary failure mechanism was fatigue. Crack initiation occurred at voids formed due to improper repair procedures and incomplete brazing. The cracks originated and propagated from stress concentration sites located in the brazed regions containing cavities. Insufficient wettability of the filler metal resulted in inadequate penetration during the brazing process, leading to localized weak bonding. Subsequent crack propagation was intensified by cyclic loading mechanisms, ultimately causing complete fracture of the stator vane. Following the stator failure, the fourth-stage rotor blade fractured under impact loading induced by foreign object damage.