The present invention is directed to a process for preparing a double metal cyanide catalyst of Formula I (M a [M'(CN) c Z w ] b ·zA), wherein M is a main group or transition metal cation, M' is a main group or transition metal cation, which can be the same or different from M, Z is an anion or ligand other than cyanide, A is an amphiphilic agent selected from heteroatom-containing organic compounds having at least one polar head group and an aliphatic, aromatic or partially aromatic moiety having a number of 6 to 42 carbon atoms, w is an integer greater than or equal to 0, but lower than c; a, b and c are integers greater than or equal to 1 so that catalyst (I) is electrically neutral, and z is a number from 0 to 12, which process comprises (a) reacting a metal salt of Formula II (M e X f ), wherein X is an anion and e and f are integers greater than or equal to 1 so that metal salt (II) is electrically neutral, with a cyanometallate complex of Formula III (D g [M'(CN) c ] b ), wherein D is a cation and g i
