OBJECTIVE AND IMPORTANCE: Although ketogenic diet therapy is effective in refractory seizures in childhood, its effect on adult encephalitis with similar refractory seizures and prolonged encephalopathy has not been well reported. CLINICAL PRESENTATION: We report here a case of a 22-year-old man with acute encephalitis with refractory repetitive partial seizures (AERRPS). INTERVENTION: Partial seizures of the face developed to repeated generalized convulsions, which were refractory against anti-epileptic drugs and a high dose of propofol. After struggling for 9 months, he dramatically recovered after ketogenic diet therapy. CONCLUSION: Ketogenic diet therapy may be an important tool to help cure AERRPS.