Objective: To assess flexural strength, color stability, surface roughness of heat cured acrylic and thermoplastic resins materials after addition of (Ag &ZrO) nanoparticles. Material and methods: One hundred specimens were prepared for this study. Fifty bars shaped specimens for flexural strength and fifty disc shaped specimens for color stability. The surface roughness was performed on the same specimens used for flexural strength. Specimenswere divided into five groups according to the denture base materials,the type and concentrations of nanoparticlesused. Three-point bending test was used to measure flexural strength. Color change was measured by spectrophotometer. Also roughness was assessed by using USB digital surface profile gauge. Results: showing significant higher flexural strength of Acrylicresinthan Flexible specimens that increased with increasing the AgNPs concentration leaded to an increase in the flexural strength of both materials than control groups, but with ZrO modified subgroup; the flexural strength decrease with increasing ZrONPs concentrations. Color showed significant changes for acrylic group than flexible group with Ag modified subgroup, but for ZrO modified subgroups, flexible group recorded significant changes than acrylic resin group. Finally, there were non-significant differences in surface roughness occurred with all groups with different nano-particle type or concentration. Conclusion: flexural strength depends on several factors including; the type of denture base, types and concentrations of nanoparticles used. Also significant color differences were detected between control group and other tested groups that were clinically unacceptable. Surface roughness of all groups showed non-significant differences.