Radiotherapy is an efficient remedy in the treatment for bladder carcinoma (BCa); still, some cancer cells can survive from the radiation; the therapeutic effect is to be improved. Regulatory T cell (Treg)-induced tumour tolerance and Akt expression play important roles in the tumour survival. This study aims to elucidate the role of radiation induces Akt expression in regulatory T cells (Tregs). The surgically removed BCa tissue was collected from 26 patients treated with or without radiotherapy. The frequency of Tregs and apoptotic Tregs in BCa tissue was assessed by flow cytometry. A cell culture model was employed to investigate the mechanism by which the tumour-infiltrating Tregs survive from radiation. After radiotherapy, the frequency of Treg was increased in the BCa tissue; the apoptotic Tregs were decreased; the expression of Akt was increased in remained Tregs. The results were reproduced in vitro with a cell culture model. The addition of Akt inhibitor blocked the radiation-induced Treg survival in culture. Akt plays an important role in the radiation-induced tumour-infiltrating Treg survival in BCa.