The effect of solution pH on the growth of spray deposited CulnS2 thin films has been investigated. Solutions with pH 1.5, 2.4, 3.5 and 4.5 are used to deposit the films on glass substrates held at 550 K. The films have been characterized using optical absorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. At pH 1.5, no film formation is observed. Films deposited from 2.4 pH solution contain binary phase Cu2S. Near stoichiometric, single phase CulnS2 films with chalcopyrite structure are formed when solution pH = 3.5. Films deposited from 4.5 pH solution are also found to be single phase, near stoichiometric CulnS2 and exhibited chalcopyrite structure. However, an additional optical absorption process is observed which is attributed to a sub-band gap absorption.