The study aims to investigate the effect of incorporation of sepiolite nanoparticles on the microtensile bond strength of an experimental dentin bonding to the human dentin. The sepiolite nanoparticles were incorporated into an experimental methacrylate-based dentin bonding system in concentrations of 0.0, 0.2, 1.0, 2.0, and 5.0 weight percents. The specimens were then ultrasonicated to finely disperse the nanoparticles in the adhesive matrix. The coronal enamel of 30 intact human premolars was cut to expose dentin. Having etched, rinsed, and blot dried the experimental bonding agents were applied to dentin surface. Adper Single Bond was used as control group according to the manufactor?s instruction. Then all the teeth were built up by composite and sectioned in stick form for microtensile test. The fracture surface was observed using SEM. The data were analyzed by ANOVA and Tukey?s post-Hoc test. The results indicated that the incorporation of the nanofiller, improved the bond strength to dentin with the highest values obtained at 1 w% sepiolite nanoparticle content. Sepiolite nanoparticles can be considered as novel fillers to improve the mechanical properties of dentin bonding agents.