Aim of the Study: To study the clinical performance and marginal integrity of high C-factor Occlusal Cavities restored with preheated Bulk-Fill, SonicFill and incremental fill composite resin. Materials and Methods: Thirty patients who required at least a triplet of class I restorations were included in the study. The patients were divided into 3 groups; Group I: Restored with preheated bulk-fill composite, Group II: Restored with SonicFill composite and Group III: Restored with Nano-hybrid incremental composite. The studied composites were evaluated clinically for the following clinical parameters: marginal integrity and adaptation, marginal discoloration, color match and surface roughness, Wear, retention of restoration, presence of secondary caries and post-operative sensitivity. Restorations were evaluated at baseline, six, 12, 18 and 24 months using modified US Public Health Service Ryge criteria and recorded as Alpha, Bravo, or Charlie. Where, Alpha corresponds to excellent, Bravo to clinically acceptable, and Charlie to clinically unacceptable results. Results: Regarding the marginal integrity, there was no statistically significant difference amongst the three tested materials except after 18 months, (P-value= 0.026). There was statistically significant difference amongst the three tested groups at 18- and 24-months evaluation where (P-value=0.031) and (P-value=0.034), respectively. No statistical significance was observed between the 3 groups regarding wear, color match, surface roughness, retention of restoration, presence of secondary caries and post-operative sensitivity. Conclusion: All tested materials showed comparable satisfactory clinical results with the exception of marginal integrity.