Aim: The study purpose was to compare the fracture resistance of different hybrid ceramic endocrown materials either with fiber reinforced composite resin base or without it. Materials and methods: Forty extracted sound mandibular molars were selected for endodontic treatment and then cut 2mm above the cementoenamel junction, Samples randomly classified into two main groups (n=20 each) according to the material of endocrown fabrication (Vita Enamic, Brilliant Crios), then subdivided into two subgroups (n=10) according to the reinforcement with composite resin base or not inside the pulp champers. CAD\CAM milling of endocrowns and cementation were performed according to manufacturer instructions. A chewing simulator was used for all samples (1,200,000 chewing cycles) in conjunction with thermocycling, then were subjected to compressive load until fracture using universal testing machine. Quantitative data was collected, tabulated and statistically analyzed using one way analysis of variance and Tukey's post hoc test. Results: There was a highly significant difference between the studied groups with the highest value of fracture strength recorded in Brilliant Crios endocrowns with FRC base while the lowest value was in Vita Enamic endocrowns without FRC base. Conclusion: Hybrid ceramic endocrowns showed an accepted fracture strength to resist the masticatory forces, while using short fiber reinforced composite base enhanced the fracture strength but without a significant value.