Aim: To evaluate various insertion techniques on the marginal adaptation of class II cavities with different composite filling materials using CLSM. Materials and method: Standardized class II cavities (MO) were prepared in eighty sound extracted human upper premolars. The cervical margin of the proximal box was located at 1mm occlusal to the cementoenamel junction (CEJ). The prepared teeth were divided into two groups of 40 teeth each and then each group was subdivided into four subgroups of 10 teeth each. The samples were subjected to etching process using 3M ESPE Scotchbond Universal etchant followed by bonding with 3M ESPE Adper™ Single Bond Plus Adhesive and then Group I was restored with 3M ESPE Filtek™ Supreme Ultra Universal, a Conventional nanohybrid resin-based dental composite and Group II was restored with 3M ESPE Filtek™ Bulk Fill Posterior Restorative,a Bulk-fill Nanohybrid high viscosity composite using four different insertion techniques.