Objective <p>To evaluate the effect of photobiomodulation (PBM), applied before or after in-office dental bleaching, on the reduction of dental sensitivity and color change.</p> Methods <p>Sixty-six participants were randomized into three groups: Control (no additional treatments before or after dental bleaching), PBM-Before (PBM applied before dental bleaching), and PBM-After (PBM applied after dental bleaching). PBM was performed with infrared light at two points (apical and cervical) on the buccal surface of the teeth. The low-power laser operated in continuous mode (100 mW power), applying 2&#xa0;J per point for 20&#xa0;s. Bleaching treatment was performed using 35% hydrogen peroxide (3 sessions with a 1-week interval). The visual analog scale evaluated dental sensitivity during dental bleaching and up to 72&#xa0;h after each session. Color was assessed at baseline and one week after the 3rd session.</p> Results <p>The PBM-Before group did not differ statistically from the PBM-After group (<i>p</i> &gt; 0.05). The PBM-Before group had lower dental sensitivity than the Control up to 1&#xa0;h after the 2nd (<i>p</i> = 0.01) and 3rd bleaching sessions (<i>p</i> = 0.01). The PBM-After group showed lower dental sensitivity than the Control at the following times: during gel application in the 2nd (<i>p</i> = 0.03) and 3rd sessions (<i>p</i> = 0.006); up to 1&#xa0;h after the 1st, 2nd, and 3rd sessions (<i>p</i> = 0.04, <i>p</i> = 0.007, <i>p</i> &lt; 0.001, respectively); and between 1 and 24&#xa0;h after bleaching in the 2nd (<i>p</i> = 0.005) and 3rd sessions (<i>p</i> &lt; 0.001). PBM did not affect the bleaching outcome (<i>p</i> &gt; 0.05).</p> Conclusion <p>PBM reduced dental sensitivity, with better results when applied after bleaching, without compromising color change.</p> Trial registration <p>NCT06518629 (2024-07-15).</p>