Zinc sulphide–reduced graphene oxide (ZnS–RGO) nanocomposite structures with varying sulphur content were synthesized by a simple solvothermal process. The various ZnS–RGO nanocomposite structures were characterized by XRD, SEM, TEM, Raman spectroscopy and field emission (FE) techniques. The SEM images revealed that the size of the ZnS nanospheres was in the range of ∼500–2000 nm. Field emission (FE) measurements on the various ZnS–RGO nanocomposite emitters were carried out in an ultra-high vacuum (UHV) environment (P < 1 × 10⁻⁸ mbar). The highest current density of ∼1490 μA cm⁻² was recorded from the nanocomposite at an applied field of 6.40 V μm⁻¹. The fluctuations in the field emission current were within 15%. Due to higher current density and lower fluctuations in the emission current, the ZnS–RGO nanocomposite material could find useful applications in the development of efficient vacuum nano electronic devices and flat panel displays.