Aim: This clinical study was conducted to evaluate the bone height changes around implant in implant supported complete mandibular overdenture. Subjects and methods: Twelve completely edentulous patients were selected for this study controlled from any systemic or local disease that may contraindicate implant placement. History taking, extra and intraoral examination, 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 by picking up the metal house into the denture. The Radiographic evaluation for the marginal bone loss was done using Digital panoramic X-ray film from the apex of the implant to most coronal points of bone attachment mesially and distally. The bone height was calculated by subtraction of it from original bone length, and the average length of both mesial and distal sites was calculated. 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: Significant bone height occur for comparisons between any follow up times more than 6 months, except between 3 and 12 months follow up. Conclusion: Significant peri-implant bone height changes occur in mandibular implant supported overdentures that increases with time.