The crystallographic orientation relationship between α and β phases during the non-equilibrium heat treatment of a Cu-37 wt. % Zn alloy was investigated. With this aim, Cu-37 wt. % Zn alloy plates with a thickness of 2 mm were heated at 810 °C for 1 h and then were quenched in water. The microstructure and texture of heat-treated samples were analyzed using optical microscopy and electron backscattered diffraction. By this non-equilibrium heat treatment, β phase was formed on both the grain boundaries and grain interiors. In addition, the Σ3 twin boundaries acted as preferred areas for α→β transformation. The orientation imaging microscopy results revealed a Kurdjumov–Sachs (K–S) orientation relationship between α and β phases. Furthermore, the details of microstructural evolution and texture analysis were discussed.