Aim: To evaluate the flexural strength and surface hardness of chemically activated provisional polymethyl methacrylate (PMMA) resin incorporated with 2.5% zirconia, titanium, and aluminum oxide (Al₂O₃) nanoparticles after 24 hours in distilled water and 2 weeks in artificial saliva after fabrication. Materials and methods: According to International Organization for Standardization (ISO) 10477:2018, a rectangular-shaped die with 25 mm l × 2 mm w × 2 mm h and wheel shape die with a diameter of 15 mm and thickness of 1 mm were made to investigate the flexural strength and surface hardness. A total of 160 samples were prepared and categorized as groups F (flexural strength) and S (surface hardness). Groups F and S were further subdivided into two groups—group I (24 hours in distilled water) and group II (2 weeks in artificial saliva), then they were subdivided into group A (control) no nanoparticle, group II (2.5% zirconia), group III (2.5%titanium oxide), and group IV (2.5% Al₂O₃). A total of 10 samples were fabricated in each category the flexural strength test was done using a universal testing machine and the hardness test was done using a digital Vickers microhardness tester. The obtained values were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test at a significant level of p < 0.05. Results: The mean values of flexural strength of autopolymerized provisional PMMA resin control, zirconium dioxide (ZrO₂), titanium dioxide (TiO₂), and Al₂O₃ nanoparticles reinforced groups in 24 hours in distilled water were 97.96, 152.81, 140.79, and 137.85 MPa, respectively, and 2 weeks in artificial saliva were 98.43, 150.43, 141.06, and 139.00 MPa, respectively. The surface hardness of autopolymerized provisional PMMA resin control, ZrO₂, TiO₂, and Al₂O₃ nanoparticles reinforced groups in 24 hours in distilled water was 28, 33.9, 32, and 30.8 Vickers hardness test (VHN), respectively, and 2 weeks in artificial saliva were 28.7, 34, 32, and 32 VHN, respectively. Conclusion: Autopolymerized provisional PMMA resin reinforced with 2.5% zirconium nanoparticles showed statistically significant flexural strength and surface hardness than conventional provisional PMMA resin and 2.5% TiO₂ and 2.5% Al₂O₃ nanoparticles reinforced groups after 24 hours in distilled water and 2 weeks in artificial saliva after fabrication. Clinical significance: The provisional restorations are subjected to masticatory forces during function and are easily prone to fracture. The use of autopolymerized provisional PMMA resin reinforced with 2.5% zirconium nanoparticles increased the mechanical properties of the provisional restoration; hence, it can be recommended for provisional restorations to increase the life span in clinical practice.