In the title compound, K(3)[Cu(C(10)H(12)N(2)O(10)P)]·2H(2)O, the Cu(II) ion, one potassium cation and a P atom are situated on a twofold rotation axis. The Cu(II) ion is coordinated by two N and four O atoms from one bis-{[bis-(carboxyl-atometh-yl)amino]-meth-yl}phosphinate ligand in a distorted octa-hedral coordination geometry. The two crystallographically independent potassium ions exhibit different coordination environments. The potassium ion in a general position is hepta-coordinated by five carboxyl-ate O atoms, one phosphinate O atom and one water mol-ecule [K-O = 2.718 (3)-3.040 (3) Å], and the potassium ion situated on the twofold rotation axis is hexa-coordinated by four carboxyl-ate O atoms and two water mol-ecules [K-O = 2.618 (3)-2.771 (3) Å]. The water mol-ecules are also involved in formation of inter-molecular O-H⋯O hydrogen bonds.