Introduction The overdenture is an alternative to fixed implant-supported prosthesis for its relatively low-cost and in clinical cases where it is impossible to place multiple implants with appropriate number and arrangement in the arch to support a fixed prosthesis. In implant-supported overdentures, many attachments such as bars, ball, and magnets can be used. The anchorage system affects the retention and stability of the overdenture as well as the load transfer to the implant and the bone. The purpose of this study was to evaluate the exerted stresses on implants and implant–abutment interface by comparing different attachment systems used for implant-supported maxillary and mandibular overdentures using finite-element analysis. Materials and Methods Stress distribution in five different models with different attachments were evaluated using finite-element analysis. The studied attachment systems were Ball/O-ring and bar-clip attachments. Three models in mandible were studied, two implants with ball attachments, two implants with bar, and four implants connected with a bar. In maxilla, two models were studied, four implants with ball attachments, and four implants connected with bar. Forces were applied bilaterally on each model in the canine and molar region separately. The forces applied were 35N axially, 70N obliquely, and 10N horizontally. Results The ball attachments models showed the highest amount of stresses on the bone and on the implants in maxilla and mandible. The bar-clip attachment with four implants showed least stress in maxilla as well as in the mandible. The bar on four implants has better stress distribution as compared with the bar on the two implants.