The study aimed to evaluate the effectiveness of in-officebleaching and associated tooth sensitivity on application ofnano-calcium phosphate paste as desensitizing agent. Bleaching wasperformed with 35% hydrogen peroxide gel in 40 patients who wererandomly divided into placebo and nano-calcium phosphate pastegroups. Bleaching efficacy (BE) was evaluated using a value-orientedVita shade guide. Tooth sensitivity was recorded using a numericrating scale (0–4) during bleaching and up to 48 h after each session.The primary outcome of absolute risk of tooth sensitivity wascompared using the Fisher’s exact test (α = 0.05). The intensity of toothsensitivity and the efficacy of in-office bleaching were also statisticallyevaluated. No significant differences in absolute risk and intensityof tooth sensitivity were detected between the groups (p = 1.0 andp = 0.53, respectively). BE was also found to be similar between thegroups (p = 0.67). Although the use of a nano-calcium phosphatepaste associated with fluoride and potassium nitrate did not influencethe whitening outcome, but it also did not reduce bleaching-inducedtooth sensitivity