Introduction: Human teeth tend to stain from intrinsic and extrinsic factors with time. The study was aimed to assess colour change of stained enamel after the use of bleaching agents. Methods: 63 extracted human teeth were selected and soaked in the coffee solution for 7 days to stain the teeth. Then they were randomly divided into 3 groups (n = 21). The groups were divided as the control group (distilled water), group using 6% carbamide peroxide (CP6) and group using 9% carbamide peroxide (CP9). The groups of CP6 and CP9 were bleached with 0.2 ml of bleaching agent for 5 minutes daily until 14 days. Colour changes were visually recorded by using VITA Toothguide 3D-MASTER and Ocean Optics Spectrometer instrument. Results: CP6 started to show shade reduction on Day 3 (score 5), followed by a steady reduction until Day 10. Day 12 to 14 showed another steady reduction of CP6. CP9 had a larger shade reduction (scores of 2-5) from Day 1 to Day 4, followed by a steady reduction until Day 14. Spectrometer analysis shows that CP9 samples had lower absorbance unit compared to CP6 samples for both second-day and sixth-day groups. However, most changes can be observed on the CP9 samples from control to the second-day and sixth-day. Conclusion: Bleaching agent with low concentration can approach the efficacy of high concentration of bleaching agent with an extended treatment time.