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The present study compares the mechanical behavior, failure mode and microstructure of sandstone with a single infilling fracture grouted by common cement and multi-walled carbon nanotubes (MWCNTs) based cement. The mechanical properties of the samples were tested under the MTS816 testing system with the assistance of the acoustic emission system and a digital video camera. The microstructure of the grouting materials was observed using scanning electron microscopy (SEM). The results indicate that the incorporation of MWCNTs into grouting reinforces the mechanical behavior of samples at an inclination angle (α) ranging from 15° to 75°. The highest reinforcing effect occurs at α = 30° for improving the compressive strength (147.8%) and at α = 15° for enhancing the elastic modulus (99.4%). The samples show three main failure modes at different inclination angles. The addition of MWCNTs reinforces the bonding strength and shearing resistance of the grouting surface, compared with the reference group, the infilled specimen presents more fracture occurring in the final rupture mode particularly at α = 15° and 30°. SEM images further illustrate that the reinforcing effects mainly result from the crack bridging and pulled-out distribution of MWCNTs in the grouting. [ABSTRACT FROM AUTHOR]