The purpose of this study was to evaluate the microtensile bond strength of resin composite to deep dentin using two different restorative protocols. Materials and Methods: Forty-five sound permanent molars were selected to expose deep dentin. Teeth were etched with 37% phosphoric acid then rinsed. Teeth were divided into five equal groups (n=9) according to deproteinizing method. Group 1: only etching (control), Group 2 and 3: deproteinized with 10% sodium hypochlorite Group 4 and 5: deproteinized with 10% bromelain enzyme. Teeth were restored with two restorative protocols either: packable nanohybrid bulk-fill resin composite or bulk-fill flowable and packable bulk-fil nanohybrid resin composite. Teeth were stored in distilled water (37°C/24 hours) then sectioned into beams. The beams were subjected to microtensile bond strength testing using a universal testing machine at a crosshead speed of 0.5 mm/min until failure occurred. Results: There was a statistically significant difference (p<0.05) between microtensile bond strength values of different groups. Group 1 recorded the highest microtensile bond strength with non-statistically significant difference from Group 4 but a statistically significantly higher microtensile bond strength than other groups. Group 5 recorded the lowest mean microtensile bond strength. Conclusion: Deproteinization of deep dentin, either with 10% sodium hypochlorite solution or 10% bromelain enzyme solution, has no improvement effect on microtensile bond strength with the packable bulk-fill resin composite used in this study. Application of flowable bulk-fill resin composite, as a liner, has a deterioration effect on the microtensile bond strength of deproteinized deep dentin to packable bulk-fill resin composite.