Zinc sulfide (ZnS) nanoparticles powders were prepared using the sol-gel method at pH values of 5, 6, and 7.The samples were treated at 200 °C for 1 h.The X-ray diffraction (XRD) results showed that the samples have a cubic crystal structure.The crystalline size decreased to 2.22 ± 0.6 nm at pH 7 due to an increase in the micro-strain.The higher lattice parameter value of ZnS is observed at pH 7 and reached a value of 5.38 ± 0.006 Å, close to bulk ZnS's value of 5.4 Å.The synergistic effect of as-prepared ZnS with chloramphenicol (C), Gentamycin (CN), and nalidixic acid (NA) antibiotics showed significantly decreased gram-negative Salmonella typhi and gram-positive Bacillus cereus bacteria activity at pH 5 and 7.The calcinated ZnS has a good synergistic effect with NA and C antibiotics against S. typhi at pH 5 and 7.The B. cereus bacteria was sensitive to the ZnS with CN antibiotic only at pH 5 and pH 7, with zone of inhibition (ZOI) diameters of 21 and 24 mm, respectively.ZnS nanoparticles at pH values of 5 and 7 promoted the efficiency of C, NA, and CN antibiotics and they had a good impact against S. typhi and B. cereus bacteria.