The electrocrystallization of Cu–Co multilayers has been investigated by means of in situ magnetization measurements, during the electrodeposition, using an electrochemical alternating gradient magnetometer. The hysteresis loops were also recorded in situ. This allowed us to measure a magnetization efficiency, ratio of the magnetization increase to the electrical charge used. This efficiency tends to decrease as the number of bilayers increases, probably as a result of the increase in the roughness of the surface. It exhibits the same dependency on cobalt plating time as the Faradaic efficiency, which confirms that at the beginning of cobalt deposition, hydrogen evolution is the main reaction. The multilayers exhibit a typical ferromagnetic behavior. The magnetization increases and the coercive field decreases when the number of bilayers and/or the thickness of the cobalt layer increase.