Statement of problem: Resin composites are one of the most popular tooth colored restorative materials. Their enamel and dentin bonding ability are based on many factors, including elasticity and filler concentration.Purpose: This study was undertaken to evaluate the effect of volumetric filler percentage and modulus of elasticity of six composites by measuring shear bond strength to dentin of the bovine teeth as experimental bonding substrate.Materials and Methods: Eighty bovine incisors were prepared and divided into eight groups. Tetric Ceram, Tetric Flow, Compo glass F, Helimolar RO, Definite, and Degufill Mineral were applied respectively. A fifth generation of dentin bonding system [Single Bond (3M, USA)] was used for all the groups. The volumetric filler percentage of each composite was obtained from their specification data. The modulus of elasticity was determined, using the formula presented by Bream et al. (1986). Then, in last two groups Heliomolar RO and Definite were bonded using their own bonding systems, Syntac Multicomponent, and Definite Multibond. The shear bond strength was measured according to the ISO/TR 11405. Pearson’s correlation test was used to compare the result with groups 4 and 5.Results: The results indicated that the relationship between both the filler percentage and the modulus of elasticity with the shear strength was 16% (P<0.005). There was a significant difference between groups 4 and 7, but no significant difference was observed between groups 5 and 8.Conclusion: Using composites with a higher filler content and modulus of elasticity resulted in higher shear bond strength in dentin bonding system. Our results showed that the corresponding dentin bonding system of composites had better results.