A 60-year-old man who developed rhabdomyolysis and severe acute kidney injury (AKI) after the fourth coronavirus disease 2019 mRNA vaccination, necessitating renal replacement therapy (RRT). The patient presented to the hospital two days post-vaccination with muscle pain in both lower extremities and anuria. Diagnostic tests revealed elevated creatinine kinase (CK) levels of 160,000 IU/L and serum creatinine levels of 6.59 mg/dL, confirming AKI due to rhabdomyolysis. Intravenous therapy was ineffective, leading to the utilization of online hemodiafiltration. Following treatment, CK levels normalized, and the renal function fully recovered.