This study investigated the clinical effectiveness and safety of sealed bleaching compared to conventional in-office bleaching using a randomized clinical trial of split arch design. Ten participants received a chairside bleaching treatment on the upper anterior teeth, and each side was randomly designated as sealed or control side. A mixture of Brite powder (PacDent, Walnut, USA), 3% hydrogen peroxide and carbamide peroxide (KoolWhite, PacDent, Walnut, USA) were used as bleaching agent. The control side was unwrapped and the experimental side was covered with a linear low density polyethylene (LLDPE) wrap for sealed bleaching. The bleaching gel was light activated for 1 hour. The tooth shades were evaluated before treatment, after treatment, and at one week check up by means of a visual shade (VS) assessment using a value oriented shade guide and a computer assisted shade assessment using a spectrophotometer (SP). The data were analyzed by paired t-test. In the control and sealed groups, the visual shade scores after bleaching treatment and at check up showed statistically significant difference from the preoperative shade scores (p<.05). The shade scores of the sealed group were significantly lighter than the control immediately after bleaching and at the check-up appointment (p<0.05). Compared to prebleaching status, the ${\Delta}E$ values at post bleaching condition were $4.35{\pm}1.38\;and\;5.08{\pm}1.34$ for the control and sealed groups, respectively. The ${\Delta}E$ values at check up were $3.73{\pm}1.95\;and\;4.38{\pm}2.08$ for the control and sealed groups. ${\Delta}E$ values were greater for the sealed group both after bleaching (p<.05) and at check up (p<.05). In conclusion, both ${\Delta}E$ and shade score changes were greater for the sealed bleaching group than the conventional bleaching group, effectively demonstrating the improvement of effectiveness through sealing.