In this work, electrochemical metallization memory (ECM) devices with an Ag/AgInSbTe (AIST)/amorphous carbon (a-C)/Pt structure were irradiated with 14 MeV neutrons. The switching reliability performance before and after neutron irradiation was compared and analyzed in detail. The results show that the irradiated memory cells functioned properly, and the initial resistance, the resistance at the low-resistance state (LRS), the RESET voltage and the data retention performance showed little degradation even when the total neutron fluence was as high as 2.5 × 10¹¹ n/cm². Other switching characteristics such as the forming voltage, the resistance at the high-resistance state (HRS), and the SET voltage were also studied, all of which merely showed a slight parameter drift. Irradiation-induced Ag ions doping of the a-C layer is proposed to explain the damaging effects of neutron irradiation. The excellent hard characteristics of these Ag/AIST/a-C/Pt-based ECM devices suggest potential beneficial applications in the aerospace and nuclear industries.