Background: The aim of this study was to evaluate the effect of two different concentrations of titanium dioxide nano particles TiO 2 NP on the color and surface roughness of enamel surface. Material and methods: 20 bovine anterior teeth were selected. Each tooth was divided into two equal halves and distributed to two groups A and B. Group A: one half is subjected to bleaching agent (AI) and the other half to bleaching agent mixed with 5% TiO 2 NP (AII). Group B: one half is subjected to bleaching agent (BI) and the other half to bleaching agent mixed with 10% TiO 2 NP (BII). Surface roughness (Ra) and color changes were evaluated using stereomicroscope and spectrophotometer. Results: There was no statistically significant difference in the roughness Ra between all bleaching groups at (p=5981>0.05). 10% concentration of TiO 2 NP group represented the lowest mean color value while there was no statistically significant difference in bleaching only groups and 5% concentration TiO 2 NP group using Pair-wise Tukey post-hoc (p>0.05). Conclusions: Titanium oxide nano particles had an influence on the efficiency of bleaching agent without jeopardizing enamel surface roughness.