Zinc sulfide is a II-VI semiconductor with a large direct band gap (3.5 eV) in the near-UV region. It has found use in a variety of applications ranging from electronic devices to biology. Production of ZnS nanoparticles by spray pyrolysis has also been reported previously. However, to date, there are no reports on synthesizing ZnS NPs by spray pyrolysis using a single-source precursor. In this work, we demonstrate preparation of ZnS nanoparticles (NPs) by spray pyrolysis using inexpensive and commercially available zinc diethyldithiocarbamate as a single-source precursor. Solutions of this precursor in toluene are dispersed into fine droplets by an atomizer and then carried by nitrogen into a tube furnace where they evaporate fully and ZnS NPs nucleate from the vapor phase. The synthesized NPs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectroscopy, UV adsorption spectroscopy and photoluminescence excitation (PLE) spectroscopy. The NPs are range from 3 – 20 nm in diameter. The HRTEM analysis clearly shows the NPs are crystalline, as indicated by the lattice fringes and selective-area electron diffraction pattern (SAED). Hexane dispersions of them exhibit bright blue emission under UV illumination. The PL emission ranges from 300 nm to 500 nm. The UV adsorption spectrum shows peaks in the range of 340-380 nm. The reaction mechanism was investigated by the online measurement of particle size distributions using a scanning mobility particle spectrometer.