Gold selenide (AuSe) is a multilayer compound that has yet to be thoroughly studied. The colloidal synthesis and characterization of gold selenide nanoparticles are described, emphasizing the effect of different gold-to-selenium precursor ratios and temperatures on the crystal structure and form. The structural characterization is done using an X-ray diffraction pattern. The coexistence of the α- and β-AuSe phases is observed in all synthesized samples. Our research indicates that the β-AuSe phase was predominantly found in the AuSe preparation process, which involved the reaction of metallic gold with elemental Se in oleylamine at a 1:1 precursor ratio of Au/Se. On the other hand, the mixed phase, which was dominated by the α-phase, was found in the selenium-rich synthesis, which had a 1:4 precursor ratio of Au/Se. The morphologies of the mainly α-AuSe sample are nanobelts, whereas the primarily β-AuSe phase sample has a nanoplate-like structure, according to the TEM and SEM data. All of the samples had Raman vibrational modes with mixed phases. The effect of high pressure on as-prepared AuSe samples has been studied in this work. The introduction of external pressure and temperature allows both phases to transition. The rising pressure reduces the presence of β-phase in the mixed phase sample, which has a pre-dominating α-phase, leaving only a substantial α-phase in the AuSe sample. The phase transition pressure was observed using Raman scattering. Our findings show that 2D AuSe has a lot of promise for multifunctional applications, encouraging more research on these systems.