Aim: to evaluate the clinical performance of an alkasite restorative material (Cention N) compared to amalgam fillings. Materials and Methods: Thirty Patients having two similar moderate class I carious cavities of posterior teeth on different sides of the same arch and with the same order were selected. A split-mouth design was adopted. Restorations were handled, finished, and polished according to manufacturer instructions. The restorations were evaluated following the revised FDI (International Dental Federation) criteria. The restorations were evaluated regarding retention/fracture of the restoration, marginal integrity, postoperative sensitivity, and patient view. The patients were recalled for evaluation at baseline (one week from the last restoration), after six months, after one year, after two years, and after three years. Statistical analysis was performed. Results: For marginal integrity and retention/fracture resistance of the restoration, there was no statistically significant difference between the two groups in all recalls or even in the same group over time (Pvalue = 1, Effect size = 0). Post-operative sensitivity and patient view results revealed a statistically significant difference between the two groups (P-value <0.001). In all recalls both restorations were clinically acceptable. Conclusion: Cention N is an acceptable alternative to amalgam in class I cavities of posterior teeth