The Co/MoS2 system may constitute a fundamental building block for future spintronic devices based on a single MoS2 transition metal dichalcogenide monolayer. Here, the hcp Co(0001)/MoS2 interface electronic structure as well as magnetic properties are investigated by first principles calculations based on the density functional theory. The charge transfer due to covalent bonding between S and Co atoms at the interface has been calculated for the lowest energy configuration obtained after optimization of the atomic coordinates. This charge transfer is different for majority and minority spin electrons, which induces a magnetization of the MoS2 layer bellow the Cobalt contact. The connection between the charge transfers at the interface and the modification of the magnetic properties is discussed.