Purpose: To compare the biomechanical responses of a normal mandible to an osteoporotic mandible with two-implant–supported magnetic attachments. Materials and Methods: A 3D finite-element model of a two-implant–supported mandibular overdenture with magnetic attachments was developed, and normal and osteoporotic bone samples were prepared. Four types of load were applied to the overdenture in each model: 100 N vertical and oblique loads on the right first molar, and a 100 N vertical load on the right canine and incisors. Biomechanical behaviors of the peri-implant bone, implant, and mucosa were recorded. Maximum equivalent stresses and elastic strains were analyzed. Results: Equivalent elastic strain in osteoporotic cortical and cancellous bone was 9% to 71% and was 142% and 207% greater than in normal cortical bone, respectively. Equivalent elastic strain in the first molar oblique loading condition was 101% to 190% greater than in the first molar vertical loading condition. Conclusions: Osteoporotic cancellous bone was weaker and less resistant to deformation than normal bone, and oblique loading was more harmful than vertical loading.