Colloidal Cu2CdSnS4 nanocrystals were synthesized by a facile solution chemistry method. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis-NIR absorbance spectroscopy measurements indicated that the Cu2CdSnS4 colloidal nanocrystals have uniform size-distribution and good crystalline quality with a tetrahedral coordinated structure. The stoichiometric ratio Cu/Cd/Sn/S is about 2.07:0.75:1.26:3.92 in Cu2CdSnS4 nanocrystals, and the chemical states of Cu, Cd, Sn and S elements are of +1, +2, +4 and -2, which correspond with the states in the molecular formula of Cu2CdSnS4. The band gap of Cu2CdSnS4 nanocrystals is estimated to be ~1.3 eV by extrapolating method.