Recently, dental implants have had the most important role in oral rehabilitation. Peri-implantitis is considered a common complication of dental implants. Adjacent natural teeth with untreated endodontic pathology may be a potential risk for implant placement. Retrograde/periapical peri-implantitis (RPI), the inverting of the progress direction of peri-implantitis. Radiographically, it is characterized by signs of periapical bone loss and normal coronal osteointegration of the implant; and its prevalence is closely associated with endodontic lesions of adjacent teeth. Another novel separate disease entity is known as the endodontic peri-implant defects (endo-implant defects), manifesting as the peri-implant marginal bone loss due to endodontic pathology of adjacent teeth, to which endodontists and implantologists are supposed to attach great importance. This current study presented two cases of different types of peri-implant infection in which conducting proper intervention to the endodontic lesions of adjacent teeth resulted in full radiographic and clinical resolution of peri-implant defects.