Objectives: This in-vitro study was conducted to evaluate the effect of different activation techniques of two in-office bleaching systems on color change of enamel surface. Materials and Methods: Thirty extracted human central incisors were collected, then embedded in a plastic mold using self-cure acrylic resin. Specimens staining was performed by immersion in red tea solution for 15 min/5 cycles per day for 5 days. Each 10 specimens were grouped according to the technique used for bleaching activation: Group A bleaching without light-activation (chemical conventional activation); Group B: LED-activated bleaching (BEYOND Polus Whitening Accelerator); Group C: Diode laser-activated bleaching (SIROLaser Blue). Each activated group was subdivided into two subgroups according to the bleaching agent used: Opalescence Xtra BOOST 40% for subgroups (A1, B1, and C1) and BEYOND MAX 5 for subgroups (A2, B2, and C2). Crystal Eye spectrophotometer was used to digitally analyze the tooth color changes following different bleaching techniques. Data was tabulated and statistically analyzed using IBM SPSS software package version 24.0 at p≤0.05, and comparisons were performed using One Way ANOVA followed by Tukey`s post hoc test. Results: C2 exhibited the highest color change value (∆E) (10.89 to 15.85) with highest bleaching effect. Following closely was A1 (12.15 to 15.65). On the other hand group A2 exhibited the lowest color change (4.380 to 9.380) with the lowest bleaching results. Conclusion: Diode laser at low power densities can be considered as an effective and reliable treatment option for bleaching of teeth.