Four new complexes, [Cu(Cpf)2](CH3COO)2∙5H2O (1), [Co(Cpf)2](CH3COO)2∙5H2O (2), [Pb(Cpf)2](CH3COO)2∙4H2O (3) and [Ag(Cpf)2]NO3∙2H2O (4) were prepared by the reaction of chlorpyrifos with Cu(CH3COO)2∙H2O, Co(CH3COO)2∙4H2O, Pb(CH3COO)2∙3H2O and AgNO3 in ethanol, respectively. The complexes were characterized by melting point, Magnetic moment, Molar conductivities, elemental analyses measurements, IR and UV-Visible spectroscopy. The obtained data indicate that chlorpyrifos interacted with metal ions in its neutral bidentate fashion. The thermal degradation (TGA and DTG) of chlorpyrifos and its metal complexes were carried out in the range 30 – 800C and the decomposition mechanisms were proposed. The data obtained agreed quit well with the proposed structures and showed that the complexes were finally decomposed to the corresponding metal oxide or metal. The free base and its metal complexes were tested for their acaricidal activity by the Dipping method. The preliminary data showed that the complexes were less toxic than chlorpyrifos.