The tensile properties, deformation mechanism, and fracture behavior of the GH4975 superalloy, were investigated using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and other advanced characterization techniques. The results show that the deformation mechanism of the alloy transitions from strong coupling dislocation shear at low temperatures to stacking fault and microtwin formation at intermediate temperatures. At temperatures higher than 850 °C, the dislocation bypass mechanism is activated and gradually dominates the dislocation movement with increasing temperature. Carbide cracking dominates the failure of the alloy at low temperatures. As the temperature increases, the grain boundary strength decreases, leading to grain boundary cracks becoming the primary crack sources. At temperatures above 800 °C, the reduction in grain boundary strength and the activation of the dislocation bypass mechanism are the primary reasons for the rapid decline in alloy strength.