Oil to be recovered is confined in tiny pores within rock, often sandstone. Oil recovery becomes more complicated when it copes with carbonate reservoirs. Carbonate reservoirs are categorized as oil-wet with low permeability. Hence, applying some technologies to decrease heavy oil viscosity and alter wettability to more water wet state is one of recent important issues. Breakthroughs in nanotechnology open up the possibility of moving beyond our current alternatives for energy supply by introducing more efficient, inexpensive and environmentally sound technologies. The current study aims to investigate the effect of nanoparticles on heavy oil viscosity, wettability alteration and steam assisted gravity drainage (SAGD). The cores being examined in the current research were categorized in two types involving: sandstone and carbonate (limestone) formed in cylindrical plugs, which their diameters were 3.8 cm and their length are 7.5 cm. The cores were prepared from the Iranian heavy/ medium oil reservoirs. The absolute permeabilities of the sandstone and carbonate samples were 122 mD, 107.44, 6.038And 0.309 mD, respectively. The porosity ranges of both samples types were between 11 and 26%. The heavy oil samples (API=13) were obtained from Iranian heavy oil fields. In the first phase of the current research, the effect of nanoparticles on heavy oil viscosity was studied. Three metal oxide nanoparticles, involving: ZnO, and CuO were used in the experiments performed in the current research. The results identified that all nanoparticles reduced the heavy oil viscosity at low concentration and high temperatures. Results showed that there were the optimum concentration (0.2wt %) for each nanoparticles in which the minimum heavy oil viscosity takes place. In the second phase, the effect of three nanoparticles on wettability alteration were examined. The experimental results showed that ZnO and CuO nanoparticles were succeeded in altering the wettability toward water wet area more than through spontaneous imbibition (SI). The interesting point was that the wettability alteration occurs for all sandstone and carbonate cores. The oil recovery for carbonate core was zero% of IOIP. Whereas, the oil recovery was 6.92, 4.2 and 8.89 for CuO, and ZnO, respectively. That trend was valid for sandstone cores. Also, the behavior of SAGD process without nano and with ZnO and CuO nanoparticles influence on heavy oil recovery were studied. It is shown that the initial stage of production is sensitive to the location of steam injection well. The larger vertical spacing between the injection and production horizontal wells causes to raise and generate faster steam chamber formation. Although locating the injection well near the center of the reservoir would have the advantage of supplying steam in all directions from the well. It is obvious that larger well spacing has remarkable effect on SOR and WCUT% decreasing. However, oil recovery is observed to increase when well spacing becomes larger. Whereas oil-production rate increases when the injection well is moved closer to the center. Based on nanoparticles characteristics on viscosity reduction, the final oil recovery is considerably increased compared to experiments without nanoparticles (87.93 for ZnO and 80.072 for CuO).