Peri-implantitis is an emerging problem, and corrective therapy requires a method for decontaminating the complex surface structure of the implant body and sterilizing the surrounding tissue. The erbium:yttrium-aluminum-garnet (Er:YAG) laser has proven to effectively allow tissue to regenerate when used for peri-implantitis. The power of the Er:YAG laser is absorbed by a water molecule; therefore, its target neither rises in temperature nor carbonizes. An antibacterial remedy based on the bacteriologic diagnosis, followed by debridement and sterilization of the implant surface and peri-implant tissues by Er:YAG laser is efficacious for periimplantitis treatment. The aim of this report was to present the effectiveness of the Er:YAG laser for peri-implant bone regeneration. This case series of two patients showed that antibiotic therapy reduced the bacterial amount from the periimplantitis sites significantly and that Er:YAG laser therapy, along with the bone augmentation, enhanced bone regeneration in the peri-implant bony defects.