Various materials have been used for core build-up when restoring the coronal portion of the tooth. Currently, bulk-fill resin composites have been produced to restore a large posterior cavity in single increment. This study aimed to evaluate the compressive strength, flexural strength, and microhardness of three commercial composite core build-up materials. All data were analyzed by oneway ANOVA and Tukey test methods (α=0.05). Flexural strength data were subjected to Weibull statistics analysis. All three groups presented significant differences in the compressive strength, flexural strength, and Knoop hardness. Filtek TM Z350 XT had the greatest compressive strength (MPa) and Knoop hardness while Filtek TM bulk fill had the highest flexural strength. MultiCore ® Flow had the lowest properties; however, it revealed the highest Weibull modulus (m) value. With regard to the properties tested in this study, bulk-fill resin composite can be used as an alternative to conventional resin composite for core build-up material.