The impact of the sintering process, especially in terms of sintering temperature and sintering aid concentration, on the ohmic transport and electrode performance of (La0.80Sr0.20)0.95CoO3–δ–gadolinia-doped ceria (LSCF-GDC) cathodes is studied. The ohmic and charge-transfer kinetics exhibit a highly coupled Co3O4 concentration dependency, showing the best performances at an optimum range of 4–5 wt%. This is ascribed to small grain sizes and improved connection between particles. The addition of Co3O4 was also found to have a dominant impact on charge-transfer kinetics in the LSCF-GDC composite layer and a moderate impact on the electronic transport in the current-collecting LSCF layer. Care should be taken to avoid a formation of excessive thermal stresses between layers when adding Co3O4.