Peroxide from bleaching agents can cause external cervical resorption. An intracoronal barrier is used to prevent leakage of bleaching agents into the periradicular space. This study aims to determine and compare the amount of peroxide released, during non vital bleaching at the end of 1st and 3rd day using Glass ionomer cement (GIC), Mineral Trioxide aggregate (ProRoot MTA) and Biodentine as intracoronal barriers. Forty-five single-rooted teeth were selected for the study and root canal therapy was performed. Three millimeters of the coronal gutta-percha were removed and according to the coronal barrier placed, samples were divided into Group A: GIC, Group B: ProRoot MTA, and Group C: Biodentine. Nonvital bleaching was done using sodium perborate and 30% H2O2. Peroxide released at the end of the 1st and 3rd day was analyzed using potassium iodide and ultraviolet spectrophotometer. This was done using the Wilcoxon matched pair test and the Kruskal-Wallis test. No significant difference in intergroup comparison at the end of 1st and 3rd day, respectively (P > 0.05), a significant difference was found in the MTA group at follow-up dates (P < 0.05). All the three tested materials (GIC, MTA, and Biodentine) may be preferred as intracoronal barrier for nonvital bleaching.