Aim: The purpose of this study was to compare the marginal accuracy and fracture resistance of endodontically treated mandibular premolars restored with endocrowns using two different monolithic CAD/CAM ceramic materials. Materials and Methods: Twenty freshly extracted human mandibular premolars were sectioned coronally and were prepared for endocrown restorations. The teeth samples were randomly assigned two groups (n =10): (LD) lithium disilicate (IPS E-max CAD) and (SH) resin hybrid ceramic (SHOFU Block HC). The CEREC AC system was used to create CAD/CAM endocrown restorations. With dual cured adhesive resin cement, endocrowns were cemented to their corresponding tooth samples. After cementation, marginal gaps were measured using a stereomicroscope, and fracture resistance for each sample was tested using a universal testing machine. Each endocrown sample's mode of failure was assessed. Data was recorded using computer software and statistically evaluated using the student t-test and the Chi square test. Results: There were no statistically significant differences in margin adaptation across the tested groups, although the E-.max CAD (LD) group had a statistically significant higher fracture resistance mean value (1022.83±127.68 N) than the Shofu HC (SH) group (659.50±110.79 N). LD group showed catastrophic fracture, while 50% of SH composite hybrid ceramic samples showed favorable fracture. Conclusions: Even though that LD endocrowns had higher fracture resistance than SH endocrowns, the mode of Shofu HC Hybrid ceramic material was more favorable than LD.