Xanthan gum (XG), a versatile biopolymer, is extensively utilized as a rheology modifier in diverse industries ranging from food and cosmetics to oil and gas. Then, the rheological response of XG under various thermophysical circumstances can be significantly influenced by the inclusion of nanomaterials like graphene oxide (GO). The goal of this work is to investigate how the rheology and microstructure of XG aqueous suspensions are affected by the addition of GO nanosheets. To assess the impact of GO concentration in an aqueous XG suspension at various pressures and temperatures, the rheological response was investigated using steady-state and oscillatory flow tests. Additionally, samples containing sodium chloride close to saturation were examined. The results indicate that addition of GO into XG suspension produces a more structured suspension with an increase in shear viscosity and viscoelastic moduli, as well as thermal stability at high temperatures, although at high pressure, a slight tendency to reduce viscosity has been observed. In contrast to GO, the addition of sodium chloride showed a decreased viscosity and viscoelasticity at low temperatures and a minor effect at high temperatures. A phenomenological model with two power-law regimes was used to fit flow curves. The cryomicrographs provided a visual representation of the microstructure of the suspesions and corroborated the rheological results. The noted improvements in shear viscosity, viscoelastic characteristics and thermal stability present encouraging avenues for the creation of sophisticated functional fluids.