||The endoplasmic reticulum (ER) is a continuous membrane network in eukaryotic cells composed of the nuclear envelope, the rough ER and the smooth ER. ER performs many important functions, including the translocation of proteins across the ER membrane, the folding of proteins in the ER lumen, the transport of proteins to the Golgi apparatus, the synthesis of lipids and steroids, and the regulation of Ca2+ concentration. The novel protein transmembrane and coiled-coil domain family 1 (TMCC1) belongs to the TMCC family. In human, this family includes at least three members (TMCC1, 2 and 3), all of which containing both coiled-coil domains and transmembrane domains, and TMCC proteins share high similarity of protein sequences. TMCC1 is conserved in different kinds of organisms from nematode to human. In this work, we characterize the novel protein TMCC1. TMCC1 is widely expressed in various types of human cells. With immunofluorescence microscopy, we find that overexpressed TMCC1 localizes to the ER, while endogenous TMCC1 localizes to the rough ER. The C-terminal transmembrane domains of TMCC1 are responsible for the ER targeting, and the N-terminal region resides in the cytoplasm. In addition, through the large coiled-coil domain, TMCC1 may form both homo- and hetero-oligomer with TMCC proteins. These results suggest that TMCC1 may play a role in protein recruitment to the ER membrane, regulation of local membrane motility, and intermembrane connection.