Introduction: About 90% of implant failures occurs in the posterior region, in association with high occlusal load. The posterior area of the oral cavity presents more occlusal loading than the anterior area with lower bone quality. Materials with low modulus of elasticity and high resiliency were suggested to reduce the occlusal stresses that are transferred to the bone-implant interface in order to simulate the shock absorbing action of the resilient periodontal ligament. Aim: Evaluation of stress distribution in implant retained fixed partial posterior prostheses, constructed from CAD/CAM Polyetheretherketone and Zirconia. Material & methods: The lower left second premolar and second molar of an acrylic cast were prepared to receive implant supported fixed partial prostheses. Five axis dental milling machine (DWX-52D) was used to mill ten fixed partial denture prostheses. The milled prostheses were grouped into two groups (n=5); group A (zirconia) and group B (PEEK). The strain gauges were attached around each implant mesially, distally, buccaly and lingually. The universal testing machine was used to apply the force at the mid pontic region of each prosthesis. Data were analyzed using Student and Paired t- test at p ≤ 0.05. Results: The highest mean microstrain (με) value was reported with the PEEK samples (3585.3±35.32) and the lowest value was reported with the zirconia samples (988.3±20.05) around the second premolar. The highest mean microstrain (με) value was reported with the PEEK samples (3803.5±21.52) and the lowest value was reported with the zirconia samples (1469.7±26.44) around the second molar. Conclusions: Different prostheses materials produce different stress patterns around dental implants.