In this paper, the variation of the Young’s modulus with plastic deformation during unloading in a tensile test with has been determined for a wide range of Dual-phase steels, covering from DP 1400 to DP 780. As a general rule, the higher strength steels have a lower variation (8%) and as the strength decreases, this diminution increases, arriving to 20%. However, in the softer steels, there are appreciable differences in young’s modulus variation although their mechanical properties are very similar. In order to explain this, the role of ferrite content in the DP steels and the presence of bainite have been analyzed as well as the initial dislocation density and its evolution with plastic deformation.