The effect of cobalt and aluminum addition on the bainitic transformation of super bainitic steels was investigated. Nanostructured bainitic ferrite and retained austenite microstructures were obtained when the steels were transformed at low temperatures. The bainitic transformation was accelerated by the addition of Co and Al. The thickness of bainite plate was reduced and the volume fraction of bainite was increased in the Co and Al containing steel, compared with the parent steel.