Aim: This clinical study was conducted to evaluate the effect of using different denture base material on masticatory efficiency in implant supported complete mandibular overdenture. Subjects and methods: Twelve completely edentulous patients were selected for this study according to inclusion and exclusion criteria that affect implant success or masticatory system. History taking, clinical, and radiographic evaluation were done for each patient. Preoperative cone beam computerized tomography (CBCT) was done for each to determine bone height and width. Each patient received two implants in the inter-foraminal area of mandible, three months later lower denture was converted into mandibular overdenture. Patients were grouped in two groups Group I: patients were received a complete mandibular overdenture constructed of conventional heat cured acrylic resin denture base. Group II: patients were received a complete mandibular overdenture constructed of flexible denture base material (polyamide). Evaluation of masticatory efficiency were done for each group by calculating chewing numbers and times. All evaluations were done at the time of implant placement, three months, six months, twelve, eighteen and twenty-four months of implant placement. One-way ANOVA with post hoc turkey test was used for multiple time comparison. Results: The chewing number and times was non-significant between the two groups. Conclusion: The denture base has no effect on masticatory efficiency of mandibular implant supported overdentures.