BACKGROUND: Leukemia inhibitory factor (LIF) is an indispensable factor for maintaining mouse embryonic stem (ES) cell pluripotency. A feeder layer and serum are also needed to maintain an undifferentiated state, however, such animal derived materials need to be eliminated for clinical applications. Therefore, a more reliable ES cell culture technique is required. METHODOLOGY/PRINCIPAL FINDINGS: We cultured mouse ES cells in simulated microgravity using a 3D-clinostat. We used feeder-free and serum-free media without LIF. CONCLUSIONS/SIGNIFICANCE: Here we show that simulated microgravity allows novel LIF-free and animal derived material-free culture methods for mouse ES cells.