OBJECTIVES: The aim of this study was to compare the amount of tooth colour change, rebound rate and tooth sensitivity in patients submitted to a bleaching technique with 6% hydrogen peroxide (HP) with or without 2% nano-hydroxyapatite (n-HA). METHODS: Sixty subjects were included in this examiner-blinded, randomized clinical trial using a 6% HP gel with or without 2% n-HA. Tooth colour and tooth sensitivity were analysed before and after treatment. All data were analysed statistically. RESULTS: After bleaching, both treatments demonstrated significant improvements in tooth shade (P < 0.05 for both groups). At the 9-month recall, tooth shade remained significantly lighter than at baseline (P < 0.05 for both groups). However, a relapse of the tooth shade was observed compared with the immediate post-bleaching result (P < 0.05). 6% HP with 2% n-HA produced significantly lower sensitivity (P < 0.05) than the bleaching product without n-HA. Colour change evaluation resulted in no difference between the two groups. CONCLUSION: Both treatments demonstrated significant improvements in tooth shade. The bleaching effectiveness of the tested products was comparable. The use of 6% HP with 2% n-HA reduced the incidence of sensitivity during the bleaching treatment compared to a bleaching agent that did not contain n-HA.