The selective synthesis of Cu2SnSe3 and Cu2SnSe4 nanocrystals was achieved by a one-step solvothermal synthesis method. We also investigated the effects of different precursor sources and starting material concentrations on the phase purity of the products. Powder X-ray diffraction, elemental analysis, and magnetic susceptibility measurements were used to investigate the phase, purity, and homogeneity of the nanocrystals. This solvothermal approach is broadly applicable and may also be employed for the synthesis of other ternary or quaternary chalcogenide nanocrystals.