The effect of α- and β-cyclodextrin-Cu(II) (1:2) complexes on the hydrolysis of organic phosphates such as fenitroxon, methyl paraoxon, and paraoxon was examined in 1.0 M NaOH solution at 25℃. The hydrolysis of these phosphates was remarkably retarded by the cyclodextrin-Cu(II) complexes. The reaction proceeds via the prior formation of an adduct between the phosphate and the complex, followed by the nucleophilic attack of the hydroxide ion on the reaction site of the phosphate included within the void space of the complex. The reaction mechanism is the same as that for the phosphorothionate ester-cyclodextrin-Cu(II) complex systems. However, the observed substrate specificity in the cyclodextrin-Cu(II) complex catalysis, which retards the hydrolysis of organic phosphates to a greater extent than that of the corresponding phosphorothionate esters, was opposite to that in the cyclodextrin catalysis.