SUMMARY Objectives: This double-blind randomized clinical trial evaluated tooth sensitivity (TS) and the effectiveness (EF) of two types of bleaching agents (Trèswhite Ortho [TWO] and Trèswhite Supreme [TWS]) when used in patients wearing orthodontic appliances. Methods and Materials: Forty patients between the ages of 18 and 40 years were randomly stratified, with an equal allocation rate, into two groups (n=20), according to the bleaching agent applied. Tooth color of the six maxillary anterior teeth was measured before and after the treatment with a spectrophotometer. The TS was recorded on three scales before and during the bleaching treatment. Results: With regard to EF, a significant reduction was found (ranging from 7.3-9.6 and 5.3-9.5 Vita scale units for TWO and TWS, respectively, p<0.001); however, there was no statistical difference between the groups (p>0.63). The number of patients with sensitivity was 58.8% and 73.3% for TWO and TWS groups, respectively (p=0.53); however, with each of the three scales used, the intensity of sensitivity was low and there was no statistical difference between TWO and TWS (p>0.05). Conclusions: In spite of producing a side effect of low TS, the two bleaching treatments tested were effective for dental bleaching in patients with fixed orthodontic appliances.