Objectives: The aim of this in vitro study was to evaluate the bleaching efficacy of high concentration bleaching agents activated by chemical or physical catalysts. Materials and methods: This study was divided into two parts. Part 1 evaluated the efficacy of tooth whitening after treatment with 35% hydrogen peroxide (Whiteness HP Maxx) that was activated by different light-curing units: halogen lamp (conventional and bleach mode) (Optilux 501C, Demetron/Kerr), LED first generation (Ultrablue IV, DMC), LED/diode laser (Ultrablue IV, DMC), LED second generation (Bluephase 16i, Ivoclar Vivadent), and no light source (control group). Part 2 provided an analysis of the effect of chemical and physical catalysts on high concentration bleaching agents: 35% hydrogen peroxide (Whiteness HP Maxx) + 20% sodium hydroxide; 35% hydrogen peroxide + 7% sodium bicarbonate; 38% hydrogen peroxide (Opalescence Xtra Boost); 35% hydrogen peroxide + halogen lamp; 35% hydrogen peroxide + 20% sodium hydroxide + halogen lamp; 35% hydrogen peroxide + 7% sodium bicarbonate + halogen lamp; 38% hydrogen peroxide + halogen lamp; and 35% hydrogen peroxide. Blocks obtained from human molars were randomly divided into groups (n = 5) in accordance with bleaching treatments. The efficacy of bleaching was measured using a spectrophotometer. Three bleaching sessions were performed. The results were submitted to ANOVA followed by the Tukey test (5%). Results: For both parts of the study, activated vs. non-activated bleaching did not differ significantly for all sessions tested. Conclusion: Activating systems did not improve the whitening effectiveness of high concentration bleaching agents.