The room-temperature crystal structure of the title compound, [Cu(H2pmida)(phen)]·3H2O [where H2pmida2− is hydrogen N-(phosphonomethyl)iminodiacetate, C5H10NO7P2−, and phen is 1,10-phenanthroline, C12H8N2], was recently determined by Pei Lu, Ke, Li, Qin, Zhou, Wu & Du [Struct. Chem. (2004), 15, 207–210]. We report here a redetermination, at 180 (2) K, with greatly improved precision. Hydrogen bonds lead to the formation of one-dimensional tapes which run along the [100] direction of the unit cell. Adjacent tapes are interconnected via π–π offset stacking (between the 1,10-phenanthroline ligands) and by hydrogen bonds involving the water molecules of crystallization.