Aim: estimate flexural strength of strengthened denture base resin by different concentrations of Zirconium oxide nanoparticles (Zro2 Nps), Aluminum oxide nanoparticles (Al2o3 Nps) and Titanium oxide nanoparticles (Tio2 Nps). Subjects and methods: fifty sample were got ready to experimentation of flexural strength together with dimensions 65 length x 10 width x 2.5mm thickness and then these samples were split into 4 series (A, B, C, D) and these groups then partitioned to 3 sub collections (1, 2, and 3) of 5 specimens for each group according to the ratio of Zro2Nps, Al2o3 Nps and Tio2 Nps which were (1%, 2% and 3%) for each type of nanoparticles that were added to heat-cured Poly methyl methacrylate (PMMA). Results: Regardless to metal oxide type, totally the highest mean value was recorded for control group < /div> (77.96 MPa). The difference between groups was statistically significant as indicated by ANOVA test (p=<0.0001<0.05) for flexural strength. Conclusions: It was found that there is slight decreasing in transverse strength of PMMA for all concentrations added of Zro2Nps, Al2o3 Nps and Tio2 Nps when compared to control group.