Greases are widely used for variety of applications at extreme pressures, temperatures and speeds with obligation of high bearing and shaft life with low noise. The present study deals with the development of nano-composite greases and record their flow and frictional characteristics. The commercial grease is modified, by dispersing nanoparticles, to get the nano-composite greases. Reduced graphene oxide (rGO), calcium carbonate (CaCO3) and alpha-alumina (a-Al2O3) are used as nano-additives. The microstructure of newly developed greases are examined using high resolution transmission electron microscopy (HRTEM) and the presence of different chemical functional groups are explored using Fourier Transform Infrared Spectroscopy (FTIR). Further, the new greases are investigated for rheological, consistency and tribological behavior using Visco Tester, penetrometer and elastohydrodymanic (EHD) rig, respectively. The flow properties reveals the shear-thinning, yielding and thixotropic nature of lubricating greases. The study shows that there is an optimality in concentration of different nano-additives above which grease' flow and tribological performance degrades. Up to 35%, 27% and 10% reduction in coefficient of friction is recorded for optimum concentration of rGO nanosheets, CaCO3 and a-Al2O3 nanoparticles, respectively. The difference in the performance of nano-composite greases can be attributed to the appearance of different friction mechanism for different nano-additives.