Purpose: To evaluate the effect of two second generation LED Light curing units and a third-generation polywave LED Ligth curing unit at three different irradiation durations on surface microhardness and detpth of cure of nano-hybrid composite resin material. Materials and Methods: EliparTM S10, EliparTM Deep Cure-S, VALO Cordless, was evaluated at 10s, 20s, 40s curing periods in this study. A nano-hybrid composite FiltekTM Z550 that contains camphorquinone as photoinitiator is used as test material. For microhardness test ninety 6 mm diameter, 4 mm deep cylindrical composite blocks in teflon molds were prepared. For each light source at each application times 10 specimen were prepared (n=10) and tested. Also ninety, 4 mm diameter, 6 mm deep cylindrical composite specimens in a split aluminum mold polymerized with three different light sources at three different durations (n=10) were tested for depth of cure measurement. Data were analyzed statistically by SPSS (Ver: 22.0) one-way ANOVA and multiple comparisons were performed by Tukey’s post- hoc test. A p-value less than 0.05 was considered statistically significant. Results: The values of cure depth were found significantly higher at 40 seconds of irradiation time for all light sources used (p<0.05). Elipar Deep Cure-S showed the higher top surface microhardness at 40s polymerization (p<0.05) Conclusions: All light devices used in the study provided adequate polymerization of the nano-hybrid composite at all application durations in this study. The highest polymerization depth and microhardness values were achieved at 40 sec. polymerization time for all LCUs.