Given the need to reduce mass in products to reduce emissions, particularly in the transportation sector, the application of adhesively bonded joints is becoming more utilised. This is very true for the emerging multi-material structures. The adhesive joint expresses good properties regarding stress distribution, sound isolation and fatigue resistance; these properties are well defined in many applications such as aircraft and car industry. However, the adhesive joints have some drawbacks in regard to the joint strength. One of the keys to strengthening joints is the surface treatment of the adherents. It is found that the surface treatments play an important role in improving the joint strength and durability. Moreover, it is also found that each adhesive material will require different types of surface treatments to make the right balance between the joint strength and fracture modes. In the current study, the adhesively bonded single lap joint (SLJ) of Carbon Fiber Reinforced Polymers (CFRP) and Aluminum (6061-T6) were subjected to a shear strength test with different mechanical surface treatments performed on the Aluminum substrate. The treated surfaces were analysed using a 3D profilometer, then the effect of surface roughness at the joint strength was investigated. It was observed that the joint strength using line patterning of 0.5 mm spacing was higher than other types of surface treatments - even compared to the baseline condition (without any surface treatment). This maybe due to the higher surface roughness, which leads to better mechanical interlocking between the adhesive material and the aluminum surface.