The tescalcin gene (Tesc) encodes an EF-hand calcium-binding protein that interacts with the sodium/hydrogen exchanger, NHE1. Previous studies indicated that Tesc was expressed in mouse embryonic testis, but not in ovary, during the critical period of testis and ovary determination. In this paper we compared the expression of Tesc in embryonic tissues of chicken and mouse. Tesc expression was sexually dimorphic in the embryonic gonads of both mouse and chicken. Tescalcin (TESC) was detected in both Sertoli cells and germ cells. In the embryonic brain of both mouse and chicken, Tesc was highly expressed in the nasal placode and in fibers extending from the olfactory epithelium to the primordial olfactory bulb. Tesc was expressed in the embryonic heart of both chicken and mouse. In mouse Tesc expression was also detected in embryonic adrenal. These studies indicate very specific expression of Tesc in various tissues in chicken and mouse during embryologic development, and conservation of Tesc expression in both species.