OBJECTIVES: The flexural strength and elastic modulus of rapidly prototyped denture base materials are affected by numerous factors including reinforcement with nanoparticles (NPs) and post-curing duration (PCD), though the effect of these two factors together has been overlooked. The present study tested the effect of nanodiamonds (NDs) or silicon dioxide nanoparticles (SNPs) with various PCDs on the flexural strength and elastic modulus of rapidly prototyped denture base materials. METHODS: To measure the flexural strength and elastic modulus, bar-shaped specimens (64 × 10 × 3.3 mm) were designed and rapidly prototyped using ASIGA and NextDent denture base resins. Each resin ( RESULTS: The flexural strength increased with prolonged PCD and the highest values for all tested groups were reported at 90 min ( CONCLUSION: The flexural strength and elastic modulus of rapidly prototyped denture base resin were increased with the addition of NDs or SNPs and when increasing the PCD. Factors including nanoparticle type and concentration, the post-curing duration, and the material type solely or in combination could affect the flexural strength and elastic modulus of prototyped denture base materials.