Thermodynamic assessment of the Cu–Zr binary system was carried out using thermodynamic data obtained over a wide range of temperatures. The associated solution model was applied to describe the short range ordering in a liquid. The glass transition was treated as a second order transition with Hillert–Jarl functions. The driving force for crystallization and time–temperature–transformation (TTT) curves were estimated from the optimized parameter set, and compared with experimental data and the results of previous thermodynamic assessments. Taking into account thermodynamic data at low temperatures, the calculated driving force was found to be lower than the results of previous assessments. Consequently, the nose of the TTT curve was shifted to a longer time.