This research was designed to study the effect of resin composite type, packing technique and C-factor on the micro-tensile bond strengths to dentin. A total of 80 sound extracted human molars were divided into two main groups (n=40), according to the resin composite type; either Tetric Evo-Ceram Bulk-Fill or Tetric Evo-Ceram nanohybrid (Vivadent Ivoclar, Schaan, Leichenstein). Each group was further subdivided into two subgroups (n=20), according to the C-factor, either high C-factor (4X4X4mm3 class I) or low C-factor (flat dentin surface). Again, each subgroup was further subdivided into two classes (n=10) according to packing technique either, bulk or incremental. The two-component self-etching AdheSE (Vivadent Ivoclar, Schaan, Leichenstein) adhesive system was utilized according to the manufacturer’s recommendations. The resin composite was applied to the cavity or to flat dentin either in one increment or in two horizontal increments, each cured for 40 seconds. The bonding and restoration procedures were performed under 20mmHg intra-pulpal pressure simulation. For standardization of the resin build ups on the flat dentin surfaces a split acrylon mold was constructed. Following storage in distilled water at 37oC under 20mmHg intrapulpal pressure simulation for 24 hours, the bonded specimens were sectioned into micro-tensile sticks which were stressed in a universal testing machine (Model LRX-plus; Lloyd instruments Ltd., Ferham, UK) till failure. Each fractured specimen was mounted on an aluminum stub, gold sputter coated and observed with a Scanning Electron Microscope (SEM) (Scanning Electron Microscope 515; Philips, Einhoven, Netherlands) at 25 KV to determine its mode of failure.Statistical analysis for the results of the study using the three-way ANOVA revealed a significant interaction among the resin composite type, packing technique and C-factor (p<0.05). One-way ANOVA revealed a significant increase in the bond