Intermediate band gap semiconductors are an underex-plored class of materials with unique optical properties of interest for photovoltaic and optoelectronic applications. Herein, we synthesize highly crystalline cubic Cu3VS4 nanocrystals with tunable edge length of 9, 12, and 18 nm. Because size control is achieved for the first time for this semiconductor, particular emphasis is laid on the structural/compositional analysis, the formation mechanism, and the size dependent optical properties. The corresponding UV-vis spectra reveal three absorption peaks in the visible range, resulting from the intermediate band gap electronic structure of Cu3VS4, which blue shift with decreasing size. Density functional theory reveals these size dependent optoelectronic properties to result mostly from weak quantum confinement. The reported results pave the way toward further fundamental investigations of the physicochemical properties of intermediate band gap semiconductors in the nanoscale regime for solar energy harvesting.