Purpose: Of this study was to investigate the fracture strength of endodontically treated teeth restored with endocrowns compared to conventional post and core supported all ceramic crowns. Materials and methods: Twenty intact extracted human mandibular premolars were selected and endodontically treated and then randomly divided into two main groups according to the type of restoration, 10 samples each. In group I, the teeth were restored by CAD/CAM all ceramic endo-crowns. In group II, the teeth were restored by fiber post and resin composite core supported CAD/CAM all ceramic crowns. All the samples were prepared using C.N.C. (Computerized Numerical Control) milling machine to standardize the preparations dimensions. A CAD/CAM system (CerecinLab) was used for indirect fabrication of all-ceramic restorations using IPS e.max CAD ceramic blocks. The fabricated all ceramic endo-crowns and crowns where then cemented using self adhesive resin cement. The samples then underwent pre-loading in a cyclic manner until fracture occurred. Results: The classical ceramic crown with glass fiber reinforced post and resin composite core group recorded higher fracture resistance mean value (2045 ± 168 N) than the all-ceramic endo-crowns group (1862 ± 254.6 N). However, the results revealed no statistical significant differences between the two test groups.