An aqueous method for the deposition of silver indium sulfide ternary semiconductor thin films is presented. According to grazing-incidence X-ray diffraction studies, a single phase of AgInS2 with orthorhombic structure or a single phase of AgIn5S8 with cubic spinel structure can be selectively grown on 3-mercaptopropyl-trimethoxysilane-modified glass substrates. As-deposited thin films were annealed for 1 h in an argon environment at 400°C in a tube furnace. It was found that when [Ag]/[In] = 1 in the precursor solution, AgInS2 was obtained. On the other hand, AgIn5S8 resulted from [Ag]/[In] ≤ 0.33 in the precursor solution. The energy gap, determined from transmission and reflection spectra, is located between 1.8 and 2.0 eV. The thickness of the thin films was in the range of 500-700 nm. Electrical resistivity was on the order of 104 Ω-cm. In addition, silver indium sulfide crystals were grown on octadecyltrichlorosilane-modified glass substrates without any post-thermal treatment. Powder X-ray diffraction and scanning electron microscope images indicated that crystalline AgIn5S8 aggregates were obtained. Detailed crystal structures, examined with a transmission electron microscope, electron diffraction, and high-resolution transmission electron microscope, further indicated that single crystals were prepared. According to these experimental findings, we were able to control compositions of silver indium sulfide thin films from aqueous solutions by suitable control of concentrations in the precursor solutions and surface functionalities. This technique provides an easy and cost-efficient way to deposit multicomponent semiconductor thin films.