Previously, we found high levels of skin-embryo-brain-oocyte homeobox (Sebox) gene expression in germinal vesicle (GV)-stage oocytes. The objective of the present study was to determine the role played by SEBOX in oocyte maturation and early embryogenesis using RNA interference (RNAi). Microinjection of Sebox double-stranded RNA into GV oocytes resulted in a marked decrease in Sebox mRNA and protein expression. However, Sebox RNAi affects neither oocyte maturation rate nor morphological characteristics, including spindle and chromosomal organization of metaphase II oocytes. In addition, Sebox RNAi had no discernible effect on the activities of M-phase promoting factor or mitogen-activated protein kinase. In contrast, microinjection of Sebox double-stranded RNA into pronuclear-stage embryos resulted in holding embryo development at the two-cell (84.9%) and the four- and eight-cell (15.1%) stages. We concluded that Sebox is a new addition to maternal effect genes that produced and stored in oocytes and function in preimplantation embryo development.