The high‐pressure and low‐temperature behaviour of the GeSexTe1−x system (x = 0, 0.2, 0.5, 0.75, 1) was studied using a combination of powder diffraction measurements and first‐principles calculations. Compounds in the stability field of the GeTe structure type (x = 0, 0.2, 0.5) follow the high‐pressure transition pathway: GeTe‐I (R3m) → GeTe‐II (f.c.c.) → GeTe‐III (Pnma). The newly determined GeTe‐III structure is isostructural to β‐GeSe, a high‐pressure and high‐temperature polymorph of GeSe. Pressure‐dependent formation enthalpies and stability regimes of the GeSexTe1−x polymorphs were studied by DFT calculations. Hexagonal Ge4Se3Te is stable up to at least 25 GPa. Significant differences in the high‐pressure and low‐temperature behaviour of the GeTe‐type structures and the hexagonal phase are highlighted. The role of Ge…Ge interactions is elucidated using the crystal orbital Hamilton population method. Finally, a sketch of the high‐pressure phase diagram of the system is provided.