The asymmetric unit of the title compound, K(I) (4)[Mo(III)(CN)(7)]·2H(2)O, consists of one [Mo(CN)(7)](4-) anion, four K(+) cations, and two water mol-ecules. The [Mo(III)(CN)(7)](4-) anion has a seven-coordinated capped-trigonal-prismatic coordination geometry. The site-occupancy factors of the disordered water mol-ecules were set at 0.90, 0.60 and 0.50. The H-atom positions could not be determined for two of the water mol-ecules. The H atoms of the water with a site-occupancy factor of 0.90 were refined using O-H and H⋯H distance restraints.