The interaction of benzoyl peroxide with nickel(O) complexes containing different tertiary phosphines has been studied. It has been shown that under the action of the nickel(O) complexes and independent of the nature of the tertiary phosphine the cleavage of either the OO or CO of benzoyl peroxide occurs. In the case of the triphenylphosphine complexes of nickel(O) the main reaction products are Ni(CO)(PPh3)3 and Ni(OCOPh)2. In the reaction of benzoyl peroxide with Ni(PEt3)4 the only reaction product is Ni(OCOPh)2(PEt3)2. In the reaction of the mixture of Ni(cod)2 and PCy3 with benzoyl peroxide the formation of the carboxylate complexes Ni(OCOPh)2(PCy3)2 or Ni(OCOPh)2PCy3 has been mainly observed. In addition, the synthesis of the carboxylate complex Ni(OCOPh)2(PEt3)2 directly from Ni(OCOPh)2 and tertiary phosphine has been carried out.