In this work, we present the influence of the reaction time of a complex substance (trisodium citrate) with a copper source (Cu2SO4 center dot 5H(2)O) on the structural, morphological and optical properties of CuS thin films deposited at 55-70 min. using chemical bath deposition onto glass substrate. In the first process, trisodium citrate and Cu2SO4 center dot 5H(2)O were mixed for 1 min, while the substances were mixed for 1 h. in the second process. The hexagonal structure of the deposited polycrystalline thin films with a preferred orientation along (130) was determined by the XRD technique except for the thin films deposited at 70 min. The surface roughnesses of the thin films were different from each other. The direct optical band gaps of CuS thin films obtained from the first process were found to be 2.39-2.45, whereas those of the second process were found to be 2.34-2.48 eV.