Objective: Hypoxia in the pulpitis process, the use of bleaching agents, and resin-containing materials pro- duce reactive oxygen species. Their damage to the pulp tissue can be eliminated by melatonin and oxyres- veratrol. However, the cytotoxic effects of these antioxidants on dental pulp stem cells are not well known. The aim of this study was to observe the cytotoxic effects of melatonin and oxyresveratrol for 72 hours on dental pulp stem cells. Materials and Methods: Human dental pulp stem cells obtained from the American Type Culture Collection were seeded on E-Plates®, and after 24 hours, 3 different doses of melatonin (100 pM, 100 nM, and 100 μM) and oxyresveratrol (10 μM, 25 μM, and 50 μM) were added. Real-time cell index data was acquired by using xCELLigence® device for 72 hours and inhibitor concentration (IC50) values of experimental groups were obtained. Analysis of covariance was used to compare the cell index values. Results: In comparison with the control group; oxyresveratrol 10 μM and melatonin 100 pM groups increased proliferation whereas oxyresveratrol 25 μM, oxyresveratrol 50 μM, and melatonin 100 μM groups induced cytotoxicity (P < .05). IC50 values at 24th, 48th, and 72th hours were 946 nM, 1220 nM, and 1243 nM for melatonin and 23 μM, 22.2 μM, and 22.5 μM for oxyresveratrol, respectively. Conclusion: Cytotoxicity of melatonin was higher than oxyresveratrol and they both increased dental pulp stem cells’ proliferation at lower doses and induced cytotoxicity at higher doses.