Protein refolding constitutes a crucial process for recombinant proteins. We report here on the development of a multifunctional refolding additive, glutathione ethyl ester (GSHEE), prepared from a redox reagent glutathione and an amino acid ethyl ester, an aggregation suppressor. Compared to glutathione, GSHEE showed 3.2-fold higher efficiency for the refolding yield of hen egg lysozyme. More importantly, a low concentration of GSHEE is more effective for refolding than conventional additives, such as amino acid ethyl esters by two orders of magnitude. The high potency of GSHEE makes it a candidate for use as a refolding additive for use in conjunction with reduced and denatured proteins.