The Polycomb group (PcG) family proteins are required for the stability of homeotic selector genes and other genes related to the regulation of mammalian development through their roles in the modulation of chromatin domains. Among them, the mammalian enhancer zeste homologue 2 (Ezh2) contributes to the transcriptional repression of these genes. Previous studies tracked the Ezh2 expression at cDNA and mRNA levels during mouse development. However, little information is known about the expression patterns of Ezh2 at the protein levels. In this study, the embryos (E6.5–E18.5) obtained through timed matings of strain Kunming mice were inserted into paraffin blocks. Tissue microarrays were constructed and followed by subsequent immunohistochemical staining. The positive cells were identified and scored based on both the percentage of stained cells and their staining intensities. Ezh2 protein expression was found throughout the embryonic tissues including the nerves, intestine epithelial, liver, pancreas, renal tubule, and lungs. Its expression level was higher at early embryonic developmental stages. However, the nerve fibers and myocardium showed weak or no immunostaining reactivities. Ezh2 protein was moderately expressed in the nuclei of renal tubule epithelial cells at E14.5. In contrast, it was weakly expressed in the fetal kidneys at E18.5 and the protein was localized in the cytoplasm of the renal tubule epithelial cells. Our data confirmed that Ezh2 protein was expressed in mouse embryos and its expression exhibited tissue specificity and dependence on the stages of embryo development. thus providing new information helpful for understanding the possible roles of Ezh2 in embryogenesis. Anat Rec, 2011. © 2011 Wiley-Liss, Inc.