The adsorption of C-60 on nickel clusters Ni-n in the n = 8-31 size range is studied at elevated temperatures. Above 800 degrees C, decomposition of C-60 is seen on clusters containing oxide impurities by the loss of CO and/or CO2 molecules. The extent of decomposition depends on cluster size and C-60 coverage, which affect the charging of the metal core by electron transfer from the metal to the C-60. Both decreased cluster size and increased C-60 coverage reduce the electron transfer per C-60 molecule, weakening the C-60-Ni-n bond and decreasing the rate of decomposition. In spite of this effect, C-60 appears to decompose more readily on small nickel clusters than on bulk nickel surfaces. While decomposition is only observed for clusters having adsorbed O atoms, the oxygen may actually inhibit decomposition by withdrawing electronic charge from the metal, likewise weakening the C-60-Ni-n bond.