We herein describe a case of a 64-year-old male mCRPC patient with somatic AKT1 and AR mutations. The patient, who had been heavily pretreated by ADT and AR inhibitors, showed stable disease progression when he received everolimus, an mTOR inhibitor. The PSA level dropped drastically from 1493.0 ng/mL to 237.6 ng/mL, after 3 months of treatment. The overall survival (OS) was 43 months, of which the progression-free survival (PFS) with everolimus treatment was 7 months.