Limited data are available on the repair bond strength between computer-aided design and manufacturing (CAD/CAM) resin nanoceramics and composite repair materials. Therefore, the purpose of this study was to test the influence of several different surface treatment modalities, intermediate agents and phosphoric acid on the shear bond strength (SBS) of repair composites with water-aged CAD/CAM resin nanoceramics. Three pretreatment and four conditioning methods comprised 12 different groups. A universal testing machine was used to test the SBS. Specimens were examined with a stereomicroscope and scanning electron microscope to determine the fracture mode. The results showed that a combination of the pretreatment and conditioning methods significantly enhanced the SBS of the resin nanoceramic (p:0.001; p < 0.01), while etching with phosphoric acid did not affect the SBS (p:0.841; p > 0.05). This study showed that surface pretreatment in combination with a conditioning method should be used in the repair of CAD/CAM nanoceramics. The highest SBS values were achieved by grinding the surface with a diamond bur followed by silane and adhesive application, whereas the lowest values were obtained in the non-conditioned non-pretreated group.