Medication-related osteonecrosis of the jaw (MRONJ) is associated with anti-resorptive drugs such as bisphosphonates (BPs) and denosumab (Dmab). These drugs disrupt bone remodeling and lead to necrosis, especially after dental procedures. Long-term steroid use in rheumatoid arthritis (RA) patients is a known risk factor that may accelerate the onset of MRONJ when combined with medicine. An 86-year-old female patient with a history of long-term steroid treatment due to rheumatoid arthritis (RA) developed peri-implant MRONJ following the Dmab treatment. The dental implants installed in the bilateral posterior maxilla had been well-maintained over 22 years. On the other hand, aggressive peri-implant MRONJ occurred four months after a Dmab injection, showing acute gingival symptoms. Through consultation with the endocrinologists, the patient discontinued Dmab. The progression of MRONJ was stabilized, and the sequestra were separated from the healthy bone margins, allowing the safe removal of sequestra. Managing peri-implant MRONJ is complex because of its multifactorial etiology and clinical presentations. Treatment ranges from conservative approaches to aggressive surgical interventions. Prevention strategies focus on oral hygiene and proactive dental care before anti-resorptive therapy. A comprehensive understanding of the patient’s medical history and systemic disease is essential. This case study revealed the possibility of MRONJ on an intact dental implant installed more than 20 years ago. Overall, an oral examination before anti-resorptive drugs (ARDs) therapy, early diagnosis, and consultation between endocrinologists and dentists are essential for effective management. This paper is expected to raise an awareness of ARDs and MRONJ for general dentists and dental practitioners. (JOURNAL OF DENTAL IMPLANT RESEARCH 2024;43(3):27-32)