This paper reports the influence of processing temperature on the microstructure of Cu2ZnSnSe4 (CZTSe) absorber layers for temperatures between 380 and 550°C produced using a 2-stage process. X-ray diffraction analysis showed the formation of Cu2ZnSnSe4 over this temperatures range. The Williamson–Hall method was used for microstructural analysis of the CZTSe absorbers, and this showed a progressive decrease of the micro-strain of the CZTSe with increasing selenisation temperature. The influence of precursor Cu content on the microstructure of the CZTSe was also studied. An increase of Cu content in the precursor is correlated to an increase in grain size and a decrease in micro-strain. Raman measurements show an asymmetrical broadening towards lower energies of the main 197 cm−1 mode for Cu-poor compositions. This study provides an insight into the dependency of the crystallinity of CZTSe on composition and synthesis temperature.