This study evaluated the repair microshear bond strength (SBS) of water stored CAD/CAM resin composite under eight different surface treatments using a silane-containing universal adhesive in etch-and-rinse and self-etching modes. In total, 48 CAD/CAM resin composite slices were prepared from Lava Ultimate CAD/CAM blocks and stored in water for 6months. The slices were assigned into 8 main groups, according to surface treatments (no treatment, no-treatment/silane, surface grinding, surface grinding/silane, sandblasting, sandblasting/silane, silica coating and silica coating/silane). Each main group was divided according to the universal adhesive application mode (either the etch-and-rinse mode or the self-etch mode). Each slice received 6 resin composite micro-cylinders (0.8x1mm). Micro-shear bond strength was run at 0.5mm/min crosshead speed until failure. Treated surfaces were examined using SEM. Bond strength data were statistically analyzed using Two-Way ANOVA/Tukey HSD post hoc test. Only surface treatment' significantly affected the repair SBS (p?0.001). Parameters Adhesive application mode' and surface treatmentxadhesive mode' showed no significant effect on SBS (p=0.458 and p=0.286 respectively). Regardless ofthe adhesive application mode, silica coating showed the highest SBS (21.6 +/- 6.8MPa), while sandblasting/silane showed the lowest SBS (13.0 +/- 6.1MPa). Regardless of adhesive application mode, the use of silica coating to treat the water-stored CAD/CAM resin composite surfaces is crucial to improve the repair bond strength.