Polymer-surfactant flooding is one of the most novel chemical enhanced oil recovery methods. Application of Nano particles in enhanced oil recovery has attracted much interest as well. This work concerns the application of Nano particles to increase the efficiency of polymer-surfactant flooding in heavy oil five-spot systems. In this investigation, micromodel setup was used to monitor the role of Nano particles on wettability alteration during polymer-surfactant floods. Two common Nano particles, SiO2 and TiO2 as well as HPAM and SDS as commercial chemicals in enhanced oil recovery, were used to create five solutions containing Nano particles at different levels of concentration. Then, contact angle tests and flooding tests were performed by taking microscopic/macroscopic pictures. According to the results, since SiO2 Nano particle decrease the contact angle more severely, it results in a higher oil recovery. Although this decrease is more when SiO2 is dispersed in water, due to its better absorption on a surface, the wettability alteration is more obvious during polymer-surfactant flooding because of the presence of a thinner oily film that intensifies mass transformation from fluid to the surface. In addition, an increase in the concentration of Nano particles leads to an increase in the efficiency of oil recovery and wettability alteration. Furthermore, according to the microscopic pictures, pulling and emulsification mechanisms are more effective than the wettability alteration mechanism.