Objective To investigate a simple, cost-effective and eco-friendly method for colorimetric detection of Hg2+ using gold nanoparticles (AuNPs) synthesized by Trichosporon montevideense WIN. Results Hg2+ induced more visible blue shift of SPR band of the AuNPs than other heavy metal ions including Pb2+, Cd2+, Fe3+, Mn2+, Co2+ and Cu2+. The lambda(max) of SPR band exhibited a gradual blue shift from 548 to 537 nm with concentration of Hg2+ increasing (0-200 mu M), and the absorbance ratio (A(537)/A(548)) showed a positive linear correlation with Hg2+ concentration (R-2 = 0.96). AuNPs synthesized at pH 6 showed more obvious blue shift than at pH 5 and pH 7. Through Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) analysis, biomolecules coated on the AuNPs were speculated to dominate the formation of a core (Au)-shell (Hg) structure, which resulted in the colorimetric response. Conclusion A sensitive and selective approach to detect Hg2+ using AuNPs synthesized by Trichosporon montevideense WIN is reported for the first time, which can provide a new potential candidate for detecting Hg2+ in the future.