In this research, the impact of trivalent oxide nanoparticles on the microstructure and performance of the magnesite-dolomite refractory bricks was examined. Up to 4 wt. % Fe2O3, Al2O3, and Cr2O3 nanoparticles were added to the specimens as additives. Physical and mechanical properties, such as bulk density (BD), apparent porosity (AP), hydration resistance (HR), and cold crushing strength (CCS) were examined. XRD and SEM analysies were used to determine the ceramic phase’s formation and microstructure analysis, respectively. Results show that the use of Fe2O3, Al2O3, and Cr2O3 nanoparticles improve the physical and mechanical properties of the MgO-CaO materials. Also, it revealed that specimens contain Fe2O3 and Al2O3 nanoparticles improve hydration resistance through the liquid phase sintering mechanism by formation of some low melting phases, such as C2F (2CaO.Fe2O3), C3A (3CaO.Al2O3), and C12.A7(12CaO•7Al2O3). But the specimens containing Cr2O3 nanoparticles improve the hydration resistance through the solid state sintering mechanism by formation phases, such as CaCr2O4 and MgCr2O4. In general, hydration resistance improvement trend of the MgO-CaO specimens includes trivalent nanoparticles is Al2O3<Fe2O3< Cr2O3.