ZFAT, originally identified as a susceptibility gene for autoimmune thyroid disease, encodes a transcriptional regulator with one AT-hook and 18 C(2)H(2)-type zinc-finger domains. It is highly conserved among species. Here, we demonstrate that ZFAT is clearly expressed in human umbilical vein endothelial cells (HUVECs). Furthermore, we show that endothelial cell assembly and the branch point formation of capillary-like structures in HUVECs is impaired by the reduction of ZFAT expression through the use of ZFAT-miRNAs, whereas differences in cell proliferation or apoptotic features were not observed after the reduction in ZFAT expression. These results suggest that ZFAT may have critical roles in the capillary-like network formation that is involved in vascular remodeling. Elucidating the ZFAT-mediated transcriptional network will lead to a better understanding of the molecular mechanisms of angiogenesis.