Synthesis of multi-component cobalt based catalysts with different metal precursors and thermal treatment was performed. A special emphasis was put on promotion with ceria. Catalysts, which were synthesized from thermally pre-activated CoCO3·mCo(OH)2·nH2O as a precursor and thereafter underwent reduction in flowing hydrogen, have a clear tendency for decomposition of mixed aluminum–cobalt containing complexes, inevitably formed during thermal treatment. The catalysts were tested in steam reforming of hydrocarbons. The size of metal particles in reduced catalysts was determined by TEM and related to catalytic activity.