We successfully established cynomolgus monkey embryonic stem (cES) cell lines expressing enhanced green fluorescent protein (GFP) by introducing a GFP-encoding gene under cytomegalovirus immediate early enhancer (CMVIE) promoter regulation into cES cells. The cells maintained the ability of in vitro differentiation toward ectodermal, mesodermal, and endodermal lineages, and produced teratomas composed of tissues derived from the three embryonic germ layers when transplanted into severe combined immunodeficient disease mice. GFP expression was also observed in the differentiated cells. These GFP-expressing cES cell lines are considered useful for basic research, including cell transplantation.