Aim: The aim of this study was to evaluate the effect of different surface treatment protocols of CAD/CAM composite blocks on the micro tensile bond strength of CAD/CAM composite blocks to dentin. Methods and Materials: A total of forty-eight human molars were used in this study. They were divided into four main groups (12 each) according to the CAD/CAM blocks surface treatment protocol; either with laboratory sandblasting as a control group, chairside air abrasion, phosphoric acid etching and a combination of chairside air abrasion and phosphoric acid etching. Each group was divided into two subgroups (6 each) according to the storage time either 24 hours or 6 months. Teeth were mounted into acrylic resin blocks to facilitate its usage