The X-ray crystal structure of the title compound, C8H15N3O4.H2O, at 20 K (space group P2(1)) reveals that the molecular conformation of the tripeptide is remarkably different from the water-free form (space group P2(1)2(1)2(1)) reported previously [Padiyar & Seshadri (1996), Acta Cryst. C52, 1693-1695].