Abstract: GeTe, a typical mid-temperature thermoelectric material, has attracted extensive attention owing to its excellent thermoelectric performance. However, GeTe exists as a low-symmetry rhombohedral phase at room temperature and transforms into a cubic phase upon heating. When the phase-transition temperature falls within the operating range of thermoelectric devices, the mismatch in thermal expansion between the two phases can induce thermal stress, thereby compromising device stability. In addition, the cubic phase possesses higher crystal symmetry, which is beneficial for increasing band degeneracy and promoting valence-band convergence, thus improving electronic transport properties. Therefore, stabilizing the cubic phase of GeTe at room temperature has become a critical issue in the structural design and performance optimization of GeTe-based thermoelectric materials. In recent years, with the development of high-entropy material design concepts, entropy engineering has emerged as an effective strategy for regulating the phase structure of GeTe. The introduction of multiple elements increases configurational entropy, enhances local disorder, and alters relative Gibbs free energies, thereby weakening low-temperature rhombohedral distortion and promoting the formation of the high-symmetry cubic phase at room temperature. Realizing the cubic phase is expected to alleviate thermally induced stress associated with phase transitions. Furthermore, through enhanced crystal symmetry, valence-band convergence, and intensified phonon scattering, it enables the synergistic optimization of structural stability and thermoelectric performance. This review focuses on the entropy-driven stabilization of the cubic phase in GeTe and its effect on thermoelectric performance regulation. The crystal structure characteristics of GeTe and the mechanism of the rhombohedral-to-cubic phase transition are systematically summarized. The thermodynamic basis for entropy-regulated cubic phase stabilization and its influence on the competition of Gibbs free energies are then discussed. Furthermore, the effects of the cubic phase on electronic and thermal transport properties are analyzed, and recent representative advances in high-entropy-regulated GeTe-based materials are reviewed. Finally, key challenges and future directions for entropy-regulated GeTe-based thermoelectric materials are outlined.