The joining of DC04 steel to 6016-T4 aluminium alloy is achieved by laser braze-welding using a 4047 (Al-12Si) filler wire and a brazing flux. The dissimilar joining is obtained both by welding the parent 6016 alloy to the 4047 filler wire, producing a continuous bonding without apparent macroscopic flaws, and by reactive wetting of the molten aluminium alloy on the solid steel, resulting in the formation of a thin layer of FeAlSi intermetallic compounds at the steel/bead interface. The linear strength of the assemblies can be as high as 190 N/mm, with a failure generally located in the reaction layer of the steel/bead interface. Last, the strength of the assemblies is shown to increase linearly with the reaction layer width.