Structural and electronic properties of pristine and transition metal doped ZnS monolayer are investigated within the framework of density functional theory. The pristine ZnS monolayer is showing direct band gap of about 2.8 eV. The investigated transition metal doping showed the transition from non-magnetic semiconductor to a magnetic system e.g. magnetic semiconductor for Co doped ZnS and half metal for Ni doped ZnS monolayers. The Co doped ZnS monolayer showed higher formation energy, confirming the strong bonding than that of Ni doped ZnS monolayer. The electron difference density shows the charge sharing between transition metal (Ni and Co) and S, confirming the covalent bond formation. © Springer Nature Switzerland AG 2019.