<p>This investigation systematically examines the impact of heat treatment on microstructural evolution and tensile properties of GH4738 Ni-based superalloy using multi-scale characterization methods. The results reveal that raising the solution temperature leads to larger grain sizes, whereas a higher solution cooling rate results in smaller grain sizes. The content of Cr-rich M₂₃C₆ carbides increases with rising solution temperature, and their morphology evolves from discrete granules to chains, eventually forming a continuous distribution along the grain boundaries. As the solution temperature rises, the spherical γ′ phase shifts from a bimodal to a unimodal distribution. Room-temperature tensile tests show that the main deformation mechanism is stacking fault shearing. By implementing a heat treatment process comprising sub-solvus solution (1000&#xa0;°C for 4&#xa0;h with oil cooling), stabilization, and aging treatment (845&#xa0;°C for 4&#xa0;h with air cooling, followed by 760&#xa0;°C for 16&#xa0;h with air cooling), the alloy exhibits superior overall tensile properties. Additionally, as the solution temperature increases, the fracture mode of the alloy transitions from ductile to a mixed ductile-brittle fracture. The predominant strengthening mechanism is precipitation strengthening, followed by solution and grain boundary strengthening. These findings provide valuable insights into optimizing the heat treatment regimes of GH4738 superalloy.</p>