Objective: To evaluate the effect of different concentrations of home bleaching agents; Opalescence Now 10% carbamide peroxide (Ultradent Products, USA) and Perfect Bleach 17% carbamide peroxide (Voco, Germany) on the surface hardness of two microhybrid resin composites; Filtek Z250 (3M ESPE, USA) and Point 4 (Kerr, USA). Methods: Thirty specimens were prepared using acrylic moulds (4mm diameter x 2mm thick) with 15 specimens for each material (n=5 controls; placed in distilled water for 14 days, n=5 were treated with Opalescence Now 10% carbamide peroxide and n=5 were treated with Perfect Bleach 17% carbamide peroxide). All specimens were stored in distilled water for 24 hours at 37°C in the incubator before bleaching. Bleaching procedure was carried out for 2 hours everyday for 14 days. Vickers hardness tester FV-7 (Future Tech Corp, Japan) was used to test the surface hardness after 14 days bleaching. The data were statistically analyzed with Mann-Whitney test (P<0.05). Results: All tested materials showed no significant changes in Vickers surface hardness after 14 days bleaching with 10% and 17% carbamide peroxide when compared with the control group. Conclusions: Fourteen days bleaching using 10% and 17% carbamide peroxide did not have different effect on the surface hardness of Point 4 and Filtek Z250.