Purpose: This study was aimed to asses the bleaching agent effect on the staining ability of enamel and composite resin. Methods: The overall number of samples was sixty; thirty enamel and thirty resin composite discs with thickness of 2 mm and lo mm were preformed from resin composite material (filtek Z25o), Each group of 30 specimens (enamel and composite) was divided into 2 groups according to the bleaching procedures, where the first group consisted of l0 specimens (n=l0) and was given symbol (Bl) which received no bleaching agent control group (stored in artificial saliva). The second group was given symbol (B2) which received a bleaching agent and consisted of 2o specimens (n=2o) and then was divided into two subgroups of lo specimens each according to time of immersion in the staining solution, where Tl represents immediate immersion (2h) and T2 represents delayed immersion (lweek). Results: Student's t-test was applied for comparison between ΔE To compare staining ability of enamel and composite ΔE was calculated between post bleaching and post staining for different time intervals, for control or no bleaching group ΔE between baseline and after staining. No statistically difference was showed in the results between staining ability of enamel and resin composite. Conclusion: Bleaching significantly increases the staining ability of both enamel and composite resin. Delaying exposure to staining solution does not restore staining ability to pre-bleach levels