Magnesium potassium-based phosphate (MKP) cement MgKPO4.6H2O is proposed as a promising alternative for immobilizing nuclear waste. In order to assess the long-term performance of MKP based cementitious matrices under harsh service conditions, it is important to investigate the radiation effects on the material at doses representative of service environment. In the present study, MKP cement samples were prepared by gel crystallization method and subsequently heat treated at 120 °C,400 °C,800 °C and 1000 °C. The powders of as-prepared and annealed MKP specimens were subjected to 10 MeV electron beam irradiation for 20 MGy dose. Electron irradiation resulted in the partial removal of structural water from the structure of as-prepared MKP specimen as confirmed through vibrational spectroscopy techniques. Amongst the as-prepared and annealed MKP specimens, MKP-1000 showed best radiation stability. Detailed insights on the radiation stability of these matrices are discussed.