There is a need to develop alternative disinfectants that differ from conventional antibiotics to address antibacterial resistance, along with specialized materials for biomedical applications. Herein, we report on the synthesis of zinc sulfide (ZnS) capped with chitosan (CS) to produce CS-ZnS nanocomposites (NCs), which were assayed for antibacterial activity in liquid handwash formulations. The CS-ZnS NCs were prepared using the bottom-up wet-chemical method. The role of CS as the capping agent was investigated by varying the ratio of CS with respect to the ZnS precursor. The prepared CS-ZnS NCs were characterized using complementary spectral methods: scanning electron microscopy–energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The antibacterial activities of liquid handwash (LH) formulations containing 1% (w/w) CS-ZnS NCs were tested against Staphylococcus aureus and Escherichia coli using the agar diffusion test method. This LH formulation displayed antibacterial activity against S. aureus with an average inhibition zone diameter in the range of 16.9–19.1 mm, and met the quality standards set by the National Standardization Agency. The formulated LH solutions containing CS-ZnS NCs showed antibacterial activity, which suggests that the CS-ZnS NCs have potential as an alternative active ingredient for tailored and non-irritant antibacterial LH detergents.