Objective This clinical study aimed to compare the effects of preoperative air-powder polishing and rubber-cup prophylaxis on tooth bleaching. Materials and methods Twenty-three patients with tooth discoloration were enrolled in this randomized controlled split-mouth experimental study. Before bleaching, air-powder polishing (APP) and rubber-cup polishing (RCP) techniques were applied on either side of the mouth. A 40% hydrogen peroxide bleaching agent was applied twice for 15 min for the in-office bleaching treatment. The tooth bleaching effects were assessed immediately and 1 week after bleaching. Results There were no significant differences between the prophylaxis groups with respect to all color parameters (Delta L, Delta a, Delta b, Delta SGU, and Delta E00) immediately after bleaching (p > 0.05). At 1-week assessment period, there were no significant differences between the prophylaxis groups with respect to all color parameters (p > 0.05), except Delta E00 (p < 0.05). Conclusion Immediately after the bleaching treatment, the two prophylactic techniques produced similar efficacy. One week after the bleaching treatment, the APP technique produced higher levels of color changes. Trial registration ClinicalTrial.gov ID: NCT04407910.