The aim : This study aims to evaluate and compare the microleakage between nano and hybrid composite. Materials and Methods : the sample consisted of forty extracted premolars for orthodontics purposes , class v cavities were prepared with a specific dimensions on the buccal surface. The sample divided into two groups ; group A restored by nanocomposite ( Z350) , group B restored by hybrid composite ( Z250) , after that, the samples were placed in the incubator with thermo cycling for a month ,The samples were then immersed in 0.5 % methelyne blue dye for 24 hours , each tooth was mesial-distal sectioned vertically , finally, of all samples was studied using stereomicroscope to evaluated the microleakage . Results : there was no statistical significant difference between the nano and hybrid composite according to microleakage.