Background: Most of the endodontically treated teeth often show considerable anatomic defect of the tooth structure, frequently requires good core build up material having a fracture resistance and good modulus of elasticity for longevity of restoration. In developing material market and propaganda about the same has led to selection bias because of less evidence based literature; so the study was aimed to evaluate three commercially available core materials in permanent posterior teeth through the evaluation of parameters like fracture resistance and modulus of elasticity. Aims and objectives: To evaluate the in vitro effect of core materials on the fracture resistance of endodontically treated teeth. Materials and Method: The in vitro study was planned to assess the fracture resistance and modulus of elasticity of three commercially available core materials. Each group was restored with 1) Metal modified Glass Ionomer cement (miracle mix, GC), 2) Bulk fill posterior composite(ivoclar) and 3) Ever X posterior core composite (GC) respectively. All the samples were subjected to fracture test using UTM (universal testing machine) INSTRON. The observer and testing person were blinded for the procedures. The results were tabulated and SPSS -20.0 was used for statistical analysis. The statistical test used were Mean, Standard deviation (SD), p-value, and One way Annova, Posthoc Tukey Test. Results: The fracture resistance and modulus of elasticity of three different materials were 1834.79 N& 270.08Mpa for Ever X posterior core material, 1352.49 N &207.84Mpa for bulk fill composite and 769.7N & 178.8 Mpa (very less) for miracle mix. Conclusion: The study results showed Ever X posterior core composite is the best core material followed by bulk fill composites and miracle mix. Within the limitation of this study Ever X posterior core composite is better than the other two.