Purpose: The aim of the present study was to investigate the stress distribution in the bone around a platformswitched implant with marginal bone loss. Materials and Methods: Finite element models of an implantsupported crown on a mandibular first molar were constructed and included an osseointegrated implant, a metal crown, and cancellous and cortical bone. Two kinds of abutments, conventional and platformswitched, were imported into the model. A variety of different levels of conical marginal bone resorption, from 0 to 2.0 mm in height and width, was created around the implant neck. The stresses generated in the peri-implant bone tissue were analyzed under 200 N of vertical or oblique loading. Results: The location of stress concentration extended from the implant neck toward the apex in association with increases in bone resorption depth. In the bone-resorbed models, the platform-switched implant showed lower maximum equivalent stresses in the peri-implant bone than the conventional abutment. The difference between the two implant models decreased as bone resorption increased. Conclusion: Within the limitations of this study, the results suggest a biomechanical advantage for platform switching in a condition of marginal bone resorption, but this advantage may be weakened when bone resorption is dramatic. Additional animal or clinical studies are necessary to better clarify the effects of peri-implant bone defects on the biomechanical features of a platform-switched configuration.