Abstract Water-soluble ZnS quantum dots (QDs) were synthesized using a co-precipitation method. Both undoped and Eu3+-doped ZnS QDs showed emission bands peaking at around 420nm. The highest photoluminescence (PL) quantum yield (QY) was measured to be 17% for undoped ZnS QDs capped with SiO2. Thermal neutron induced pulse height and pulse shape spectra were measured for composites composed of 6LiF nanoparticles, undoped ZnS QDs, and poly(vinyl alcohol) (PVA) matrix. The pulse height spectra from the nanocomposites were analyzed with a track-structure model. The pulse decay time of scintillation photons is 10–30ns. The fast decay rates and clear pulse height peaks induced by thermal neutrons indicate that ZnS QD based nanocomposites are promising scintillators for detecting high-flux thermal neutrons.