Rasmussen's encephalitis (RE) is a severe, rare, chronic inflammatory brain disease resulting in drug-resistant epilepsy and progressive destruction of one hemisphere with loss of neurological function. RE is associated with a deterioration of background electroencephalography (EEG) activity, a progressive atrophy on magnetic resonance imaging (MRI) imaging and an extensive positron emission tomography hypometabolism over the affected hemisphere. RE is an immune-mediated disease, with a predominant role of CD8+ T cytotoxic cells, microglial cells, and activation of inflammasome pathway. The diagnosis of RE is based on clinical (intractable epilepsy and neurological deterioration), electrophysiological (unilateral EEG slowing) and MRI (hemiatrophy) criteria. Antiseizure medications are generally unable to stop seizures. The most effective procedure is hemispherotomy (surgical disconnection of one cerebral hemisphere), but this is associated with permanent motor and neurological deficits. Treatments targeting the immune system are recommended especially in the early stages of the disease or in patients with slow disease progression and mild deficits and/or not eligible for surgery. Based on the pathophysiology, several immunotherapies have been tried in RE (none exhaustively: corticosteroid, intravenous immunoglobulins, tacrolimus, azathioprine, adalimumab, mycophenolate mofetil, natalizumab). However, only small cohorts have been reported without comparative study. In this review, we will summarise some pathophysiological mechanisms of RE, before reporting the literature data concerning immunotherapies. We then discuss the limitations of these studies and the prospects for further research.