Embryonic stem (ES) cells are pluripotent cells derived from the inner cell mass of blastocysts, and transcription factors Oct-3/4, Nanog, Sox2, and STAT3, are essential for their self-renewal. In this study, we searched for molecules downstream of STAT3 in ES cells. Using DNA chip analysis, we obtained GA-repeat binding protein (GABP) alpha. Expression of GABPalpha was restricted to undifferentiated ES cells and controlled by STAT3. We found that the expression level of Oct-3/4 is reduced by knockdown of GABPalpha. On the other hand, GABPalpha-overexpressing ES cells maintained the expression level of Oct-3/4 even in the absence of LIF. Moreover, the induction of Oct-3/4 repressors Cdx-2, Coup-tf1, and GCNF was stimulated by GABPalpha knockdown. These data suggest that GABPalpha upregulates the expression of Oct-3/4 via downregulation of Oct-3/4 repressors.