High-dose denosumab (Xgeva®) is increasingly used for treating bone metastasis and various malignant diseases but carries the risk of medication-related osteonecrosis of the jaw (MRONJ). This study aimed to evaluate the incidence, risk factors, and clinical outcomes of MRONJ in patients treated with high-dose denosumab. A retrospective review was performed on 1278 patients who received high-dose denosumab at Severance Hospital, Seoul, South Korea, from September 2014 to February 2023. Data on the incidence of MRONJ, patient demographics, primary diseases, and treatment outcomes were analyzed. Among the 1278 patients (average age 64.72years; 728 males and 550 females) treated, 34 developed MRONJ, with a 2.66% incidence rate. The average age of those with MRONJ was 68.32years, and they received more Xgeva® injections on average (13.62) compared to the overall cohort. Factors such as age and the frequency of injections were significantly associated with the risk of MRONJ. Notably, the incidence of MRONJ did not significantly differ between those who underwent oral surgery and those with spontaneous MRONJ, especially if oral surgery occurred within 1month of injection. Surgical interventions have shown higher recovery rates in advanced MRONJ stages. This study confirmed a significant MRONJ incidence of 2.66% among high-dose denosumab recipients, highlighting the importance of careful patient selection, monitoring, and education, particularly in older and long-term treatment patients, to mitigate the risk of MRONJ.