Ni doped ZnS (Zn 1− x Ni x S) nanoparticles with Ni concentration x=0.01, 0.03 and 0.05 were synthesized by the chemical co-precipitation technique. Powder X-ray diffraction (XRD) reveals that Ni incorporates into the ZnS crystal lattice with a cubic structure. Transmission electron microscopy (TEM) measurements show that the average size of these nanoparticles is in the range 2–3nm. Micro-Raman and photololuminescence (PL) studies also confirm the incorporation of Ni in the lattice. X-ray absorption spectroscopy (XAS) reveals that Ni replace the Zn atoms in the host lattice without forming second phases. The ZnS nanoparticles with lower Ni concentration exhibit saturated hysteresis loop at room temperature indicating ferromagnetism where as samples having higher Ni concentrations did not show such saturation confirming the intrinsic nature of the ferromagnetism at smaller doping.