•Cu3SbS3 nanocrystallites were obtained through a solvothermal route.•The effect of reaction time on the properties of the products was discussed.•We proposed an easy way to adjust the products׳ band gap from 0.75 to 1.2 eV.•The thioglycolic acid can also be used to prepare other nanomaterials.Cu3SbS3 nanocrystallites were successfully obtained through a facile solvothermal route at 165 °C for 8, 12, 16, 20 and 24 h, based on reactions between CuCl2, SbCl3 and thioglycolic acid in glycol. The effect of reaction time on structural, morphology and optical properties was investigated. It can be seen from the TEM images that the products grew from spherical to rhombus. The UV–visible absorption indicates a significant change in optical band gap (0.75–1.2 eV) with extending the reaction time. In addition, the proposed solvothermal method with thioglycolic acid as both sulfur source and complexing reagent provides an alternative approach to prepare other ternary semiconductor nanomaterials.