This unit describes a protocol on how to achieve high transfection efficiency on human embryonic stem cells and induced pluripotent stem cells using the common transfection reagent Lipofectamine 2000 as a carrier instead of involving a virus, and/or expensive equipment and reagents. Applying this technique for siRNA-mediated gene targeting to knockdown genes in the pluripotent stem cells, the expression of pluripotent genes, such as OCT4 and LIN28, was downregulated by more than 90% in multiple pluripotent cell lines. Beyond reaching high transfection efficiency on pluripotent cells, this protocol should also have application to primary cells that are traditionally difficult to transfect.