We introduce a hydrothermal method for synthesizing ultrafine earth abundant Cu2ZnSnS4 (CZTS) nanocrystals with an average size of 5-6 nm using simple Cu(II), Zn(II), Sn(II) inorganic salt and thiourea as precursor. X-ray diffraction, Raman spectrum and transmission electron microscopy studies indicate that CZTS nanocrystals with pure kesterite structure have been synthesized at temperature as low as 180 degrees C. The band-gap energy determined from the absorbance spectrum is 1.47 eV, suggesting that as-synthesized CZTS nanocrystals are very suitable for photovoltaic applications. (C) 2012 Elsevier B.V. All rights reserved.