Nickel-polyester composites and nickel-polyester composites modified with cobalt were used as electrodes for the oxygen evolution reaction (OER) in aqueous alkaline solutions. The influence of the aging by repetitive triangular potential sweep (RTPS) on the composite electrodes performance toward the oxygen evolution process was studied. The results obtained demonstrate that the RTPS induces the growth of the active nickel hydroxide at the aggregates of bare nickel located on the surface and in the bulk of the electrode. In the case of the composite modified with cobalt, electrochemical aging led to the formation of cobalt oxides. Morphological and physical characterisation of both unmodified and modified nickel-polyester composites was performed.