Objectives:Polymethyl methacrylate, PMMA, is widely used in prosthodontics for fabrication of removable prostheses. This study was undertaken to investigate the effect of adding silver nanoparticles (AgNPs) to PMMA at 0.5% and 2% concentrations on flexural strength, fracture toughness, impact strength, compressive strength and hardness of heat-polymerized acrylic resin. Materials and methods: The silver nanoparticles (AgNPs) were mixed with heat-cured acrylic resin with different concentrations at 0.5 and 2 wt% and processed with optimal condition (2.5:1 Powder/monomer ratio, conventional packing method and water bath curing for 2 hours at 95?C) to fabricate test specimens of PMMA of dimensions (50 ? 30 ? 30 mm) for the flexural strength, fracture toughness, cylindrical samples (25?38 mm) were prepared for compressive strength, rectangular shaped specimens (60 x 7 x 4 mm) were prepared for impact strength testing and (30 ? 10 ? 2.5 mm) were fabricated for measuring hardness. PMMA without additives was prepared as a test control. The recorded values of flexural strength in (MPa), fracture toughness in (MPa.m1/2), impact strength in (KJ/m2), compressive strength in (MPa) and hardness (VHN) were collected, tabulated and statistically analyzed. One way analysis of variance (ANOVA) and Tukey?s tests were used for testing the significance between the means of tested groups which are statistically significant when the P value ? 0.05. Result: Addition of silver nanoparticles (AgNPs) to PMMA significantly increased the flexural strength, fracture toughness, impact strength, compressive strength and hardness. Conclusion: These results indicate that of silver nanoparticles added to PMMA has a potential as a reliable denture base material with increased flexural strength, fracture toughness, impact strength, compressive strength and hardness. According to the results of the present study, the best mechanical properties were achieved by adding 2%wt AgNPs concentration.