Aim: To evaluate the marginal seal of sonic-activated composite resin using various dispensing rates in class V restorations. Materials and methods: Standardized class V cavities were performed in forty extracted sound human molars that were arbitrarily divided into four equal groups (n=10) according to the extrusion force magnitude and dispensing technique as follows: Group I (Control), manual extrusion force (FM), Group II: low extrusion force (F1) of sonic energy, Group III: medium extrusion force (F3) of sonic energy and Group IV: high extrusion force (F5) of sonic energy. Composite resins were packed inside the prepared cavities and photopolymerized. For groups II, III, and IV, a Sonic Fill handpiece was used to deliver sonic energy. While for group I, no sonic energy was used. All specimens were thermocycled, gold-sputtered, and examined under a scanning electron microscope for marginal seal assessment. Statistical analysis was done using Kruskall-Wallis and Mann-Whitney tests, with a significance level of P ≤ 0.05. Results: Group I showed higher marginal gaps (1.70 ± 0.67) compared to sonic-activated groups (p < 0.05). Marginal gaps of group II (1.0 ± 0.82) were nearly similar to that of group III (0.80 ± 0.79) (p > 0.05), while group IV (0.20 ± 0.42) revealed a significant decrease in the marginal gaps to that of group II and III (p < 0.05). Conclusions: Using the Sonic Fill handpiece at the highest extrusion force enhances the marginal sealing of SonicFill 2 composite resin restorations compared to the medium and lowest extrusion forces.