The high strength medium temperature and β metastable titanium alloy, β-CEZ, is designed for use in the compressor of a jet engine. The purpose of this research was to investigate how the thermomechanical treatments (forging or solutioning conditions and quenching) influence the microstructure. A series of various heat-treating steps were conducted in order to quantify the relationship between thermomechanical parameters and microstructural factors. The detailed characterization of microstructure was based on SEM observations of primary alpha platelets with the aid of an Image Analysis system. A pronounced influence of thermomechanical treatments on microstructure was found. Several parameters characterizing the microstructure of alpha platelets such as the area fraction, length, width, perimeter, surface, density, and aspect ratio, have been found to depend on the solutioning conditions. Furthermore, with the exception of the area fraction, these different microstructural parameters were found to be also governed by the forging conditions.