Peri-implantitis is an inflammatory disease of the peri-implant tissue by bacterial infection or other factors, which results in peri-implant bone loss. Many nonsurgical treatments were tried on initial to moderate peri-implantitis lesion to reduce the inflammation. Some of these treatments made effective results, however, they were not definitively predictable. To prevent peri-implantitis and further peri-implant bone loss, early intervention is the most important. Early detection of peri-implant infection through the regular maintenance care can make it possible to do early nonsurgical intervention. Nonsurgical intervention is effective on peri-implant mucositis and can also be effective on initial peri-implantitis lesion. If the peri-implantitis is not resolves by nonsurgical treatment, surgical approach should be considered.